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作者: fai1888    時間: 2017-4-11 13:34     標題: 松鼠

請問版友們在大嶼山有無見過松鼠?香港有無關於松鼠的研究呢?
唔該曬
作者: Aland    時間: 2017-4-25 14:03



QUOTE:
原帖由 fai1888 於 2017-4-11 13:34 發表
請問版友們在大嶼山有無見過松鼠?香港有無關於松鼠的研究呢?
唔該曬

文獻記載赤腹松鼠兩個亞種的分佈,可參考:
http://www.afcd.gov.hk/tc_chi/conservation/hkbiodiversity/database/popup_record.asp?id=3769
不過個人仍然未曾領略到如何分辨安徽及泰國亞種

作為引入種,赤腹松鼠的分佈很可能視乎當初放生的地點
故大嶼山無松鼠並不令人意外

我覺得比較奇怪的是赤腹松鼠在新界似乎相當局限於新界中部
理論上 大欖/大帽山/大埔滘 與 九龍群山/馬鞍山/西貢 並無城市帶相隔,松鼠應可散播至後面幾個大區
所以反而想問有無版友曾在新界中部以外見過赤腹松鼠?
作者: fai1888    時間: 2017-4-25 22:39     標題: 回覆 #2 Aland 的帖子

唔該Aland,唔知道漁護處引入一些新品種時候有咩野原則呢?
作者: tommy    時間: 2017-4-25 23:20



QUOTE:
原帖由 Aland 於 2017-4-25 14:03 發表

文獻記載赤腹松鼠兩個亞種的分佈,可參考:
http://www.afcd.gov.hk/tc_chi/co ... _record.asp?id=3769
不過個人仍然未曾領略到如何分辨安徽及泰國亞種

作為引入種,赤腹松鼠的分佈 ...

在落馬洲村附近見過, 另外如果你睇返香港陸上哺乳動物圖鑑, 新界西其實有record
作者: Pan Tong    時間: 2017-4-26 00:15

新界北 上水 雞嶺都有見過~
作者: Aland    時間: 2017-4-26 01:53



QUOTE:
原帖由 fai1888 於 2017-4-25 22:39 發表
唔該Aland,唔知道漁護處引入一些新品種時候有咩野原則呢?

以我所知,赤腹松鼠應該並非漁護署引入,pet release 機會較大
如果漁護署引入應該不會刻意分別引進兩種不同亞種.........

關於刻意引入物種,香港其實例子不多,以生態原因引入者更少
只知有研究嘗試用各種菟絲子克制微甘菊,引入食蚊魚控制蚊蟲數量(後者成生態災難)
其他引入、重新引入的物種,絕大部分為佛教放生、意外引入

重新引入/引入物種其實相當具爭議性
我自己原則上同意重新引入部分曾經在香港出現過的keystone species,如鼯鼠(飛鼠)、水鹿等
不過宜謹慎,否則只會重演食蚊魚所造成的生態災難

關於引入/重新引入等生態議題,我強烈推薦《香港生態情報》一書
此書絕對稱得上本地生態天書
作者: Aland    時間: 2017-4-26 02:09



QUOTE:
原帖由 tommy 於 2017-4-25 23:20 發表
在落馬洲村附近見過, 另外如果你睇返香港陸上哺乳動物圖鑑, 新界西其實有record

身在外地,我本香港陸上哺乳動物圖鑑同我相隔半個地球............

望返論壇記錄,大欖同新界北應該有
但東北(八仙嶺/船灣)、西貢似乎無記錄?未知條分佈界線在何?

另外,雖然文獻寫赤腹松鼠愛好埋藏堅果,但感覺上堅果最多的山地林從來不見其踪影
反而市區/林緣依賴培栽植物花果為生的佔大多數
赤腹松鼠對一堆堅果的傳種作用似乎有限?
作者: fai1888    時間: 2017-4-26 21:45     標題: 回覆 #6 Aland 的帖子

我都知道引進新物種要非常非常小心,好似生魚,澳洲引入toad;結果成為生態災難。松鼠應該本身香港有既,重新引進又點樣呢?
作者: fai1888    時間: 2017-4-26 21:52



QUOTE:
原帖由 Aland 於 2017-4-26 02:09 發表

身在外地,我本香港陸上哺乳動物圖鑑同我相隔半個地球............

望返論壇記錄,大欖同新界北應該有
但東北(八仙嶺/船灣)、西貢似乎無記錄?未知條分佈界線在何?

另外,雖然文獻寫赤腹松鼠愛好埋藏堅果,但感覺上堅果最多的 ...

其實我系唸緊如果重新引進原有既松鼠,睇睇會不會對殼斗科既植物多個傳播媒界,因為殼斗科植物應該原本系香港4大科之一。
作者: Aland    時間: 2017-4-26 23:09



QUOTE:
原帖由 fai1888 於 2017-4-26 21:45 發表
我都知道引進新物種要非常非常小心,好似生魚,澳洲引入toad;結果成為生態災難。松鼠應該本身香港有既,重新引進又點樣呢?

除老虎/鱷魚等對行山人士安全有威脅的物種外
重新引入locally extinct species基本上爭議不大
甚至引入外來物種代替原有megafauna都有成功例子
例如外國有不少外島在Pleistocene megafaunal extinctions裡失去了本地陸龜
近年就有計劃引入其他外來陸龜維持本地植披結構
聽聞相當成功

參考:https://theraptorlab.wordpress.com/2013/08/05/slow-steady-rewilding-with-tortoises/

反觀香港,重新引入松鼠/飛鼠等物種去幫助殼斗科、茶科等樹種傳種是有需要
但問題是究竟香港曾經有過的是甚麼物種?是否仍然存在於鄰近地區?
如果引入後繼續如赤腹松鼠般,不存在於原生密林/次生林
對本地生態其實無大幫助

其實有無人知東亞其他地區殼斗科如何傳種?

[ 本帖最後由 Aland 於 2017-4-27 00:42 編輯 ]
作者: fai1888    時間: 2017-4-27 10:43



QUOTE:
原帖由 Aland 於 2017-4-26 23:09 發表

除老虎/鱷魚等對行山人士安全有威脅的物種外
重新引入locally extinct species基本上爭議不大
甚至引入外來物種代替原有megafauna都有成功例子
例如外國有不少外島在Pleistocene megafaunal extinctions裡失去了本 ...

Aland,
  謝謝你既回覆,對了,香港曾經出現什麼品種呢?我睇過一份paper話,香港出現的兩種松鼠都系外來品種。赤腹松鼠只有在香港島出現,大概有一半它們的食物是吃外來品種植物的果,另外有1x-2x 食物來自人類,可能系佢地身處地方太多或者太容易找到食物,他們不需要到原生密林/次生林找食物。假設它們被放到大嶼山可能要找大自然的種子吃,那麼對種子傳播可能有正面作用?


“但問題是究竟香港曾經有過的是甚麼物種?是否仍然存在於鄰近地區?
如果引入後繼續如赤腹松鼠般,不存在於原生密林/次生林”
作者: Aland    時間: 2017-4-27 12:01



QUOTE:
原帖由 fai1888 於 2017-4-27 10:43 發表


Aland,
  謝謝你既回覆,對了,香港曾經出現什麼品種呢?我睇過一份paper話,香港出現的兩種松鼠都系外來品種。赤腹松鼠只有在香港島出現,大概有一半它們的食物是吃外來品種植物的果,另外有1x-2x 食物來自人類,可能系佢地身處 ...

多謝你initiate個討論就真.........

入正題

I may be overly pedantic
但嚴格而言香港只有一種松鼠——赤腹松鼠
「亞種」和「種」始終有分別
印象中亞種之間應該可以interbreed?(有錯請指正)

赤腹松鼠何以依賴人類/培栽植物為生,有幾個可能性
1. 如你所講,現有棲地無數量可觀、更「天然」的食物來源
2. 本地原生林/次生林(就算大嶼山)完全無合適食物
3. 堆松鼠來自captivity,依賴市區已成習慣
4. 原生果子狸爭食

個人認為1是2/3/4的後果,非成因
始終港島半山/嘉道理與成熟森林直接相連
要入密林棲息,太容易

2其實都未必完全講得通
安徽、泰國氣候/植披雖然與香港不盡相同
但既然松鼠可以學會食洋紫荊、木棉、朱纓花
很難想象原生樹林完全無合適食物

我覺得主因應該是3
培栽植物/人類垃圾營養價值高
一群曾經在鐵籠中生活,放生後依賴林緣/市區食物的松鼠
未必能重新適應自然環境
美國各國家公園不斷提醒遊人不要喂飼松鼠也是出於同一原因

至於4,如果是事實,其實相當值得研究
尤其赤腹松鼠自然分布與果子狸有不少重疊

當然還有一個可能性
就是樹林其實有松鼠,只是數量少我們視而不見而已
有無人手上有本香港哺乳動物圖鑑幫我查camera trap data?

[ 本帖最後由 Aland 於 2017-4-27 12:26 編輯 ]
作者: Aland    時間: 2017-4-27 12:21



QUOTE:
原帖由 fai1888 於 2017-4-27 10:43 發表

Aland,
  謝謝你既回覆,對了,香港曾經出現什麼品種呢? ...

無人可以確認,但肯定非常非常精彩
至少 短吻鱷、亞洲象、犀牛、葉猴、五間狸、赤狐、華南虎、飛鼠、水鹿、豹 應該全部都曾在香港出現過
基本上無論如何重新引入,香港的megafaunal diversity都與以往相距甚遠

其實此值得深思
既然完全無可能回復到人類大幅干預前的狀態,究竟conservation應該採取甚麼方向?
上面list入面有個別物種對維持生境多樣化 (or beta diversity)非常重要
例如大象,因為夠大力,在不少熱帶國家乃推倒樹木,逆轉演化,維持空曠生境的重要物種
以香港低地林規模,應該再難support大象
如此,阻止溼地演化成密林工作由誰負責?

[ 本帖最後由 Aland 於 2017-4-27 12:29 編輯 ]
作者: tommy    時間: 2017-4-27 13:28

好耐冇見到深入嘅討論喇~雖然我唔識植物, 但容許我吹下水~~

有關seed dispersal可以參考返學者Richard Corlettr呢篇文獻:
Seed dispersal in Hong Kong, China: past, present and possible futures
https://www.researchgate.net/pro ... 256ed8782000000.pdf
作者: tommy    時間: 2017-4-27 13:39



QUOTE:
原帖由 Aland 於 2017-4-27 12:21 發表

無人可以確認,但肯定非常非常精彩
至少 短吻鱷、亞洲象、犀牛、葉猴、五間狸、赤狐、華南虎、飛鼠、水鹿、豹 應該全部都曾在香港出現過
基本上無論如何重新引入,香港的megafaunal diversity都與以往相距甚遠

其實此值得深思
既然完全無可能回復到人類大幅干預前的狀態,究竟conservation應該採取甚麼方向?
上面list入面有個別物種對維持生境多樣化 (or beta diversity)非常重要
例如大象,因為夠大力,在不少熱帶國家乃推倒樹木,逆轉演化,維持空曠生境的重要物種
以香港低地林規模,應該再難support大象
如此,阻止溼地演化成密林工作由誰負責?

以上提過嘅動物, 有唔少係確確實實喺香港出現過
但我地已經冇辦法肯肯定咁去知道what have we lost
重新引入呢d物種, 我相信唔會係短期內(5-10年)發生, 因為有太多問題要解決
但長遠對香港次生林生境幾重要

至於第二個問題: 阻止溼地演化成密林工作由誰負責?
正正因為我地唔知道what have we lost, 好多以前發生喺本地嘅ecological process已經"失傳"
勉強要搵嘅, 水牛可以嗎?
但其實除左濕地, 仲有其他生境面臨同一個情況
好似高地嘅grassland/shrubland, 同樣support特別嘅物種(e.g.大草鶯)
但理論上呢類生境係會慢慢success到woodland
咁我地又應該點做呢? 係制止natural succession? 定由得佢?
作者: jasonpoon    時間: 2017-4-27 13:47

it is becoming "philosophical" but was a good discussion. even we think in terms of "mega" events like the first arrival of humanoids/human, change from hunter-gatherer to agriculture settlement (let go the industrial revolution which we have better knowledge of the environmental/extinction effects), we could only guess what "human" have done to the "original" megafaunal diversity of every human touched habitats, either temporary or permanent. in a way, human is but one of nature's produce... isnt it?

for times not so long ago as to involve too many natural/climatic/geologic changes (eg earthquake, tsunami, volcanic eruption, glacial activity, sedimentation... to ice age, tectonic movement... etc). the "original" megafauna should also be under continuous changes by "BDIE", competition, adaptive radiation, micro-evolution and speciation, etc.

think of some isolated places where ancient "living fossils" have survived until today. panda and ancient plants around sichuan, mammoth (until recently) of siberia, coelacanth in east africa and indonesia. lungfishes in australia, s. america & africa, it seemed that extinction of many once diversely distributed similar species in mega scale have occurred over the geological ages yet ancient characters could be preserved for so long if given the rare chance.

the key point i think is that human has the ability now to drastically change the earth with previously unseen scale and speed (like by nuclear or chemical or biological war in one extreme). but we see and seek "equilibrium" and "stability" in common sense and knowledge (whether true or false? right or wrong?). we know we have done so much irreversible things in such a short time that are ultimately of no good contribution to our own future and generations then, that we started to think conservation.

note that there are many people with totally different knowledge or ignorance out there!

we have wildlife (megafauna) poacher, trader, cook and taster, crafter and skin/shell/bone/tooth/meat/blood lover of all kinds. are we as conservationist also thought deep enough about the reason for some of these phenomenon?

we have every reason to exterminate disease causing agents (cf conservation in philosophical sense). think of the pox virus, which are now only suviving in special cell cultures in a few labs (human is its natural host that unfortunately it tends to make very ill or kill). we have done a long way to exterminate unsuccessfully one ancient species - the cockroach (have anyone marvelled about the cockroach, as a wildlife!). we are struggling with the same efforts towards many other species. of the many disease causing organisms, some are real beauties under the microscope or in culture medium. we could also learn a lot from the agility of mosquito and common fly!

on the other hand, why are dolphins being so brutally butchered in a small cove in japan? and why do they still keep on hunting whales in view of their relative high level of common education and scientific knowledge? any and what kind of political, cultural, social or criminal factors are behind this dilemma? how should we understand, tolerate, protest or condemn these activities?

why are some people keep on using, as food, tonic or medicine, elephant tusk, rhinocerus horn, seahorse, tiger bone, bear bile juice, pangolin scale, eagle & owl, tutle & lizard,... to things like shark fin, swallow nest?

as a member of the oriental race, perhaps we have some or more special feeling or understanding on these?

on the many introduced species, you have mentioned varied reasons and results, and it seemed a case by case scenario? what should be the standard or should there be any standards? consider the local wildlife and conservation mentality as examplified by our media reports on wild boar sightings and shootings, our exploding population and the desire and need for new land, the need for jobs, for security, for our children, immigrants, visitors and our own daily living... what is the outlook and direction for conservation in hk? on a smaller agenda, what message and action are in need of popularizing and promoting right now?

we have done something as i see in over 30 years as a bystander, although considered so minimal and inadequate maybe. we need to continue to do something, or more.

[ 本帖最後由 jasonpoon 於 2017-4-27 16:30 編輯 ]
作者: Aland    時間: 2017-4-28 05:27



QUOTE:
原帖由 tommy 於 2017-4-27 13:39 發表
以上提過嘅動物, 有唔少係確確實實喺香港出現過
但我地已經冇辦法肯肯定咁去知道what have we lost
重新引入呢d物種, 我相信唔會係短期內(5-10年)發生, 因為有太多問題要解決
但長遠對香港次生林生境幾重要

至於 ...

其實香港近一兩百年內仍然存在的哺乳類動物,大都在文獻內有記錄
香港有不少megafauna,其實是到二戰前後伐林摧毀>90%本地樹林的時候才在本地絕跡
至少大靈貓(五間狸)、赤狐 等幾個物種肯定曾經在香港出現過
而這類物種,其實附近地區仍然有相當可觀的族群,重新引入絕對可行

但引入這些物種究竟能否解決seed dispersal問題,值得相榷
上面你引用的文章其實都有提到,香港堅果類植物的seed dispersal應該由rodents負責
而rodents的文獻記錄遠較megafauna差
引入未能證實在香港曾經出現過的物種爭議肯定大

現時漁護署對重新引入的態度肯定是傾向謹慎
但終日話要繼續研究,要繼續研究,其實亦非可行之計
The clock is ticking,重新引入有時限,越遲做越多物種受牽連

以植物角度,數一數,原生殼斗科36種
其中3種似乎已經一段時間無出現過(白櫟、鼠刺葉柯、苦櫧)
另外17種分佈狹窄或少見樹苗(麻櫟、木薑葉青岡、油葉柯、櫟葉柯、廣南柯、耳柯、厚斗柯、尖葉柯、雷公青岡、福建青岡、櫟子青岡、檳榔青岡、吊皮錐、毛錐、栲、甜櫧、米櫧)
個人觀察,上述不少物種大有可能在一兩代內消失
其餘16種分佈比較廣而且數量稍多,有機會如某些南美evolutionary ghosts般在物種消失後存在一段長時間
但就算樹苗比較多的物種(例如竹葉青岡),亦似乎只能靠落果發芽繁衍

如果將安息香科、茶科、樟科 等納入統計
情況就更加令人擔憂

QUOTE:
至於第二個問題: 阻止溼地演化成密林工作由誰負責?
正正因為我地唔知道what have we lost, 好多以前發生喺本地嘅ecological process已經"失傳"
勉強要搵嘅, 水牛可以嗎?
但其實除左濕地, 仲有其他生境面臨同一個情況
好似高地嘅grassland/shrubland, 同樣support特別嘅物種(e.g.大草鶯)
但理論上呢類生境係會慢慢success到woodland
咁我地又應該點做呢? 係制止natural succession? 定由得佢?

米埔印象中有project用水牛維持濕地生態價值
效果如何?

香港的高山草坡生境究竟會否全部經由succession變成密林,其實是一個有趣的議題
我兩派意見都聽過,有一派覺得本地部分地區雨量/風勢可以在一定程度上阻止succession
但無論如何,succession在不少山地生境絕對正在以頗快的速度發生
而如果要在大帽山紅花嶺大幅移除林木保護大草鶯,肯定惹來反彈
甚至幾年前有關當局打毒釘殺死大頭茶保護香港杜鵑,已經引起不少爭議
外國當下流行的一個concept,rewilding,即重新引入,甚至從外來引入相關megafauna, and let them do the work
但香港一來生境規模太小,二來根本未確實知道當初高山草地、濕地究竟是何以維持
要做rewilding,未必可行
作者: Aland    時間: 2017-4-28 06:05



QUOTE:
原帖由 jasonpoon 於 2017-4-27 13:47 發表
it is becoming "philosophical" but was a good discussion. even we think in terms of "mega" events like the first arrival of humanoids/human, change from hunter-gatherer to agricult ...

I think we have to first accept a cold hard fact——no ecosystem is truly natural now. Even the Amazon rainforest was once packed with human settlements and agricultural land, and that is even before Europeans reached South America. In fact, Europeans killing off 99% of the inhabitants of South America led to such rapid forest growth that the world entered a little ice age due to falling CO2 levels from the newly sequestered carbon. If we view the fauna and flora as species all living on human disturbed habitats, with various degrees of present/past intervention, we will soon come to the conclusion that minimal intervention is not a possible way out for conservation. Locally, species that once lived in wetlands created by meandering rivers, grasslands maintained by elephants, or dense natural woodland, are now adapted to live in human created habitats such as abandoned paddies, fire-maintained grasslands, and abandoned tea plantations respectively. As we could never go back to the original state, some sort of intervention or active management is needed for the continued survival of these species. The problem is, this message is not coming through, even among naturalists, among which many still believe that conservation is, strictly, no intervention.

As for the point about what we define as 'pathogens' and 'pests'. I believe is impractical and too extreme to convince people to love the mosquitoes and cockroaches wandering around the household. However, this does raises the issue of the purpose of conservation. Is it merely to allow continued appreciation of their aesthetic value? Or is it because organisms have the intrinsic right to be living on the planet? Alternatively, as economists might be keen to point out, is conservation aimed at protecting the value of the ecosystem services provided by the ecosystem? I tend to believe that all of the above are relevant and valid reasons for conservation, but when it comes down to political decisions about whether to sacrifice conservation for development, it is often the case that some arguments for conservation are stronger than others. How should we decide what do forgo what we face these struggles? Question for everyone to ponder
作者: fai1888    時間: 2017-4-28 08:33



QUOTE:
原帖由 Aland 於 2017-4-27 12:01 發表

多謝你initiate個討論就真.........

入正題

I may be overly pedantic
但嚴格而言香港只有一種松鼠——赤腹松鼠
「亞種」和「種」始終有分別
印象中亞種之間應該可以interbreed?(有錯請指正)

赤腹松鼠何以依賴人類/ ...

越來越有趣,我都覺得系第三個原因比較似,好似猴子一樣,過渡依靠人類食物結果就唔自己找食物,並非不足夠天然食物。
  另外我昨天看過一份報告,大嶼山並不存在松鼠與果子狸。有趣地喬木比較,大嶼山只有新界的1/3喬木品種,所以數據上可能食物來源的確有頗大的限制。
果子狸是否會吃堅果? 香港植物漿果比例應該比堅果多好多,如果堅果比例多D應該就唔會競爭太激烈?
作者: jasonpoon    時間: 2017-4-28 10:21



QUOTE:
原帖由 fai1888 於 2017-4-28 08:33 AM 發表

越來越有趣,我都覺得系第三個原因比較似,好似猴子一樣,過渡依靠人類食物結果就唔自己找食物,並非不足夠天然食物。
  另外我昨天看過一份報告,大嶼山並不存在松鼠與果子狸。有趣地喬木比較,大嶼山只有新界的1/3喬木品種,所 ...

is it likely that omnivorous wild animals will try to find easy food from around human settlements. other eg include the polar bear, wolf (which becomes dog by domestication), boar (becomes pig), pheasant (becomes chicken), etc.

it is interesting that you mention the squirrals did not (or have not yet) crossed the narrow sea barriers to enter lantau. or they could not establish there due to lack of nuts? think of the Paguma that is also absent from lantau but which should be native for a much longer period, the lack of both nutty & fruity trees in lantau maybe the reason but that does not answer why the squirrels, let alone the Paguma, are absent in lantau.

squirrels are indeed a more temperate species group when their global distribution is considered. i think global warming could indeed hinder their range expansion into the subtropics or tropics.
作者: fai1888    時間: 2017-4-28 10:46



QUOTE:
原帖由 Aland 於 2017-4-28 05:27 發表

其實香港近一兩百年內仍然存在的哺乳類動物,大都在文獻內有記錄
香港有不少megafauna,其實是到二戰前後伐林摧毀>90%本地樹林的時候才在本地絕跡
至少大靈貓(五間狸)、赤狐 等幾個物種肯定曾經在香港出現過
而這類物 ...

哇,咁多物種都有危機,真系要做下野。
Aland,你提到有威脅的物種的確唔系好容易找到。
作者: jasonpoon    時間: 2017-4-28 11:18     標題: 回覆 #18 Aland 的帖子

"Even the Amazon rainforest was once packed with human settlements and agricultural land, and that is even before Europeans reached South America. In fact, Europeans killing off 99% of the inhabitants of South America led to such rapid forest growth that the world entered a little ice age due to falling CO2 levels from the newly sequestered carbon."

this hypothesis is new to me... consider european settlement from 1490's and the killing has taken its effect in 100 years and the forest expanded so fast and consumed so much CO2 globally to initiate a little ice age in 100-300 years? the 1700's to 2000's had western industralization and CO2 increase contributing to present time global warming?


"If we view the fauna and flora as species all living on human disturbed habitats, with various degrees of present/past intervention, we will soon come to the conclusion that minimal intervention is not a possible way out for conservation. Locally, species that once lived in wetlands created by meandering rivers, grasslands maintained by elephants, or dense natural woodland, are now adapted to live in human created habitats such as abandoned paddies, fire-maintained grasslands, and abandoned tea plantations respectively. As we could never go back to the original state, some sort of intervention or active management is needed for the continued survival of these species. The problem is, this message is not coming through, even among naturalists, among which many still believe that conservation is, strictly, no intervention."

yes, indeed the complexity of changes after disturbance are hardly known at all. cf. massive locusts swam as a result(?) of mass rapid killing of common sparrows in the 50's in china, extensive changes in megafauna of the yellow stone after complete hunting of wolves in the usa...

in present day hk, reintroduction of large predators or even herbivores seemed out of the question. escaped and feral dogs and cats may contribute to top predation locally that directly affect ground animals and birds population. even the wild boars are considered "pest" by some people here. many birds are poisoned and expelled by local farmers (as late as in the 80's when some farming remained). big fishes like groupers, grunters, eels, etc are hunted to extinction with trawling and sand excavation destroyed nearly all of our natural seabed. streams and rivers are dumped with agricultural waste and pesticide rich effluents that all fishes except very tough species disappeared. i see more and more "silent" beaches, bays, shores, streams, forests and lands over the years. even when i drove deep into mainland china.

released species like Tilapia sp., Xiphophorus sp., Poecilia sp., Loricarius sp., etc have extended to many streams and water bodies with little known effects.

if one of the aim of local conservation should be to identify species to re-introduce that would ultimately contribute to "restoring" perceived or recorded past conditions and diversities after "cleaning-up" of local habitats, it could be done after short studies and public consultations given the species involved are well known.

it has come to my believe that conservation is ultimately connected with politics in the short term and public understanding, views and culture in the long term. efforts nowadays insisted continuously may see significant results only in decades (cf. anti-smoking movement).

[ 本帖最後由 jasonpoon 於 2017-4-29 07:05 編輯 ]
作者: fai1888    時間: 2017-4-28 17:07



QUOTE:
原帖由 jasonpoon 於 2017-4-28 10:21 發表



is it likely that omnivorous wild animals will try to find easy food from around human settlements. other eg include the polar bear, wolf (which becomes dog by domestication), boar (becomes pig), p ...

is it easy to cross the harbour from hk island to lantau by squirrel? i think it's now with the Tsing Ma bridge,it's easier. haha. question is if they had been released by people why it didn't survive inlantau? can the conclusion be draw by no suitable food?
   if we introduce the squirrel after reforestaion of more navtive plants and fagaceae. will they survive?
作者: Aland    時間: 2017-4-29 02:16



QUOTE:
原帖由 jasonpoon 於 2017-4-28 11:18 發表
this hypothesis is new to me... consider european settlement from 1490's and the killing has taken its effect in 100 years and the forest expanded so fast and consumed so much CO2 globally to initiate a little ice age in 100-300 years? the 1700's to 2000's had western industralization and CO2 increase contributing to present time global warming?

I have looked up the original paper. More accurately, the event I was referring to the Colombian Encounter, which introduced old world diseases and killed off 95% of the inhabitants. These inhabitants were using fire based agricultural practices (火耕) before the Colombian Encounter and burnt down much of the natural forests. The population crash following the Colombian Encounter lead to a recovery of forests, drop in atmospheric CO2, and the Little Ice Age between 1550-1750. I'm not too shocked that the Little Ice Age came so quickly after the population crash. Forest regrowth could be extremely quick in the tropics, certain species could achieve heights of 40m in 5 years.

Here is the original paper for reference:
http://www.tandfonline.com/doi/abs/10.1080/00045608.2010.502432

QUOTE:
in present day hk, reintroduction of large predators or even herbivores seemed out of the question. escaped and feral dogs and cats may contribute to top predation locally that directly affect ground animals and birds population. even the wild boars are considered "pest" by some people here.

Regarding wild boars, I do understand why villagers dislike them. They destroy a significant amount of crops in fields. I actually like to think that the loss of large predators is the reason behind these problems. Without large predators, wild boars in Hong Kong seem to constantly go over its natural carrying capacity, which results in hungry boars wandering in villages or even urban areas. As much as I recognize that wild boars are an important part of the local ecosystem, such a massive population of wild boars is to some extent problematic even in a conservation standpoint. They seem to be clearing the entire understory in some of the woodlands in New Territories. I have seen woodlands with nearly no understory shrubs or plants of any kind in Fo Tan/NT northeast. I do wonder whether this is the natural state for wild boars to be so numerous and so destructive.

Nevertheless, I do agree that reintroducing large predators is a bit impractical in Hong Kong. Even if you do manage to find tigers or leopards for reintroduction, I don't think the idea would be popular among hikers and villagers living near the forest. This again, poses an interesting question. Wild boar poaching is opposed by many conservation groups. If indeed wild boars are not supposed to be that numerous, are programs controls the wild boar population as 'evil' and 'unethical' as we've originally thought?
作者: jasonpoon    時間: 2017-4-29 07:03



QUOTE:
原帖由 Aland 於 2017-4-29 02:16 AM 發表

I have looked up the original paper. More accurately, the event I was referring to the Colombian Encounter, which introduced old world diseases and killed off 95% of the inhabitants. These inhabitant ...

this is worth more thinking... if rapid "global cooling" could happen in such a case by the (rapid) re-growth of tropical forest the size of, say, half or one-third of the amazon, then countries in the tropics having previous large rain forests could theoretically help save the present day global warming by reforestation. consider the increasing budgetary spending by the present day governments and industries, the reward and incentive for reforestation maybe good enough to be practical... given its global CO2 reduction efficacy being proven. similar thinking on whether the ocean could be a giant CO2 reservoir has been proposed decades ago but seemed not fashioned in latest news.

the population dynamics of local wild boars should therefore be studied fast and detailed enough to allow more informed conservation decision. is local farming (in the traditional way) virtually non-existent now in hk? i do not know about the present views of farmers toward boar disturbances but they are of some concern for birds, insects and boars even the Red Muntjac back in the 80's. if and how are the few "organic" farms today bothered by those "pests" are not known to me.
作者: Aland    時間: 2017-4-29 08:13



QUOTE:
原帖由 fai1888 於 2017-4-28 08:33 發表
越來越有趣,我都覺得系第三個原因比較似,好似猴子一樣,過渡依靠人類食物結果就唔自己找食物,並非不足夠天然食物。
  另外我昨天看過一份報告,大嶼山並不存在松鼠與果子狸。有趣地喬木比較,大嶼山只有新界的1/3喬木品種,所以數據上可能食物來源的確有頗大的限制。
果子狸是否會吃堅果? 香港植物漿果比例應該比堅果多好多,如果堅果比例多D應該就唔會競爭太激烈?

當松鼠依靠人類/培栽植物為生後,population size會增長,我會相當懷疑天然環境能否支撐現有的松鼠population
反而有趣的是,赤腹松鼠自然分布其實相當接近香港
華南其他地區的赤腹松鼠究竟靠甚麼食物維生?(進而引申到,香港本來有無赤腹松鼠?)

另外你提到獼猴,多口講兩句
雖然人類食物佔獼猴food intake的一部分,但實際上獼猴亦花不少時間在林中覓食
尤其大埔滘、西貢的群族,基本上沒有人刻意喂飼
印象中有記錄獼猴取食黃牙果、山橙、以及數種外來植物(白花鬼針草、狗牙根)
而我個人見過獼猴取食斜葉榕葉片、大頭茶果實
除了金山長期有人喂飼之外,其他獼猴群族可能無想象中依賴人類

最後大嶼山問題
大嶼山不僅沒有松鼠和果子狸,更沒有小靈貓,只有善於游泳的野豬
究竟大嶼山是盤古初開已經無tree dwelling mammals,還是曾經存在過但之後locally extinct?
而以大嶼山規模,又實在比較難想象果子狸/小靈貓雙雙在港島生存下來,而大嶼山一種不留
你hypothesize大嶼山樹種少所以難支撐樹棲食果動物,並非不可能
但想問你有無份報告更詳盡的資料提供?因為據個人觀察大嶼山樹種不少.........
作者: Aland    時間: 2017-4-30 00:52



QUOTE:
原帖由 jasonpoon 於 2017-4-29 07:03 發表



this is worth more thinking... if rapid "global cooling" could happen in such a case by the (rapid) re-growth of tropical forest the size of, say, half or one-third of the amazon, then co ...

The carbon dioxide concentration decrease that likely contributed to the Little Ice Age is in the magnitude of 5-10ppm. The carbon dioxide increases after the industrial revolution is in the magnitude of 100-120ppm. Reforestation programmes are helpful, but I'm afraid they are insufficient to even maintain the carbon dioxide concentration at current levels (400ppm) given the high rates of carbon dioxide emissions. Not to mention that once forests are cut down and converted into human settlements/farmland or even cities, it is simply politically impossible to force people to abandon their land in a large scale.

Regarding the debate about whether the the oceans or the forest is more important in sequestering carbon dioxide. Yes, oceans are storing enormous amounts of carbon dioxide in dissolved solution form, much more than what the forests or terrestrial biomes are storing. However, I think it is meaningless to compare the absolute amount of carbon stored. Instead, we should focus on whether these systems have the potential to pull down what is in the atmosphere, i.e. net carbon sequestration. Regarding the flow of carbon between the atmosphere and forests/oceans, the numbers are as following:

Forests: 120Gt of carbon pulled down by photosynthesis, but net photosynthesis (subtracting respiration) is around 62.5Gt. Decomposition in forests account for another 60Gt release in carbon dioxide. Hence the net carbon sequestration is about 2.5Gt.
Oceans: Amount of carbon that enters the oceans is around 92.5Gt, but around 90Gt comes back out. The net 2.5Gt carbon sequestration is attributed to marine organisms, especially algae. Algae received much attention in recent years because it pulls down less carbon dioxide than forests (only around 50Gt) but achieved similar net sequestration as forests, likely due to its extremely high turnover rate.

I would say that forests and oceans sequester similar amounts of carbon if left undisturbed, both systems together contribute to a net carbon sequestration of 5Gt a year. There are indeed programmes to try to increase the ocean net carbon sequestration by fertilizing the oceans with iron to promote algal growth or storing carbon into rocks, but many of these programmes are unrealistic (If you allow me, fertilizing the sea is just stupid) and I have reservations in whether these programmes could save us.

At the end of the day, cutting the 7Gt fossil fuel+deforestration/habitat conversion emissions is really the key, but sadly, as you've mentioned, we're definitely not doing enough.

QUOTE:
the population dynamics of local wild boars should therefore be studied fast and detailed enough to allow more informed conservation decision. is local farming (in the traditional way) virtually non-existent now in hk? i do not know about the present views of farmers toward boar disturbances but they are of some concern for birds, insects and boars even the Red Muntjac back in the 80's. if and how are the few "organic" farms today bothered by those "pests" are not known to me.

I agree that the wild boar population dynamics should be studied. To convince people that wild boar going over it's carrying capacity is an issue to be dealt with, we need solid data, and educated guesses, like the ones I have stated in #24, are hardly enough to convince the authority to take action. The problem is, we simply don't know enough about the past. How effective are tigers/leopards in controlling the wild boar population? What is a 'health' population of wild boars? It is virtually impossible to obtain data from the past and make a case that the current situation is problematic..........
作者: fai1888    時間: 2017-5-2 21:31



QUOTE:
原帖由 Aland 於 2017-4-29 08:13 發表

大嶼山不僅沒有松鼠和果子狸,更沒有小靈貓,只有善於游泳的野豬
究竟大嶼山是盤古初開已經無tree dwelling mammals,還是曾經存在過但之後locally extinct?
而以大嶼山規模,又實在比較難想象果子狸/小靈貓雙雙在港島生存下來,而大嶼山一種不留
你hypothesize大嶼山樹種少所以難支撐樹棲食果動物,並非不可能
但想問你有無份報告更詳盡的資料提供?因為據個人觀察大嶼山樹種不少.........

唔好意思,呢排好忙遲左覆,以下就係個報告

圖片: lantau-spcompare.low.jpg (2017-5-2 21:31, 59.98 K) / 該附件被下載次數 43
http://www.hkwildlife.net/Forum/attachment.php?aid=53008


作者: mathew    時間: 2017-5-4 20:09

差啲miss左呢個咁高質既討論

無論是出於什麼原因, 重新引進物種的風險太高. 某程度上難以評估所帶來的影響/連鎖反應.

至於有些植物若因為欠缺傳播/授粉的動物而不能自然繁殖, 何不由人手培育再種回野外.
地點選擇可以是早年的植林, 無必要取締日漸稀少的草地生境.

保育不應理解為絕不干涉, 特別在香港如此密集的地方, 適當管理是必要的.
問題是
1. 何謂適當?
2. 信任管理者嗎?

#28 似乎係一個2003既研討會, 希望可以睇到全文(似是以下題目)再作討論
大嶼山的植群分布現況與其在香港生態保育之地位
The Vegetation of the Lantau Island and its Conservation Concerns
作者: jasonpoon    時間: 2017-5-5 00:36

another point: it was said many years ago by the then mainly foreign naturalists that the "fung shui" woods at the back of villages are of special interest as they may resemble the "original" flora as they are untouched due to traditional culture. any good study has been done on the surviving fung shui woods in hk?
作者: Xoni    時間: 2017-5-5 01:18



QUOTE:
原帖由 Aland 於 2017-4-29 08:13 發表

當松鼠依靠人類/培栽植物為生後,population size會增長,我會相當懷疑天然環境能否支撐現有的松鼠population
反而有趣的是,赤腹松鼠自然分布其實相當接近香港
華南其他地區的赤腹松鼠究竟靠甚麼食物維生?(進而引申到,香港 ...

可以參考一下:

"The most striking feature of the geographical distribution of larger mammals in Hong Kong is the absence of many species from Lantau I., despite its relatively large size (144 km2) and rugged topography that has confined development to a narrow coastal strip. The absence of macaques and tree squirrels probably reflects the absence of deliberate introductions, while the absence of the small Indian mongoose and yellow-bellied weasel is also not surprising if they have colonized Hong Kong only recently. However, Lantau also has neither civet species, nor leopard cats or porcupines, all of which occur on the smaller (78 km2) and more-developed Hong Kong I. It is possible that some of these species were never present on Lantau I., but it seems more likely that they were extirpated and have been unable to recolonize across the marine barrier, although this does not explain their survival on Hong Kong I. Indeed, porcupines have been recorded on several islands of < 2 km2 in area (Reels 1996). Within the mainland New Territories, which supports all of the recorded mammal species, most species are widespread, except for those that are likely to be recent invasions or introductions."

Pei, K. J.-C., Y.-C. Lai, R. T. Corlett, and K.-Y. Suen. 2010. The larger mammal fauna of Hong Kong: species survival in a highly degraded landscape. Zool. Stud. 49 (2): 253-264.

http://wildmic.npust.edu.tw/ezfiles/60/1060/img/1408/253.pdf
作者: Aland    時間: 2017-5-5 03:19



QUOTE:
原帖由 mathew 於 2017-5-4 20:09 發表
差啲miss左呢個咁高質既討論

無論是出於什麼原因, 重新引進物種的風險太高. 某程度上難以評估所帶來的影響/連鎖反應.

重新引入,代表該物種曾經在香港出現過
理論上所帶來的影響/連鎖反應,只是還原香港生態系統的舊貌?
有無實驗可以評估重新引入的物種對本地生態的影響?
如香港公園觀鳥園般,在一片本地樹林內用一個鐵網去contain一群準備重新引入的物種,藉此觀察其feeding pattern/interaction with other local species,又是否可行?

QUOTE:
至於有些植物若因為欠缺傳播/授粉的動物而不能自然繁殖, 何不由人手培育再種回野外.
地點選擇可以是早年的植林, 無必要取締日漸稀少的草地生境.

保育不應理解為絕不干涉, 特別在香港如此密集的地方, 適當管理是必要的.
問題是
1. 何謂適當?
2. 信任管理者嗎?

樓上#14的論文入面,其實都有建議在現有的灌叢/植林栽種自然更新能力低的物種

我自己就覺得,作為小規模/短期措施,去避免部分物種在短期內本地滅絕,或者改善本來生態價值低/植披結構簡單的植林,絕對可行
但個人認為,這類措施其實長遠而言並不能取替動物在天然樹林內的角色,亦好難大規模做,理由有幾個:
1. 不合符成本效益,雖然香港地方相對外國不少natural reserves細,但不規則地在全港各種生境引入a mixture of plant species成本可能比植林更高
2. 可以預期計劃只會集中於主徑/容易到達的生境,對維持香港整體植披結構效用成疑
3. 一個生境不存在指定植物物種,有時可能是生境不適合其生長所致,由人手改變植物自然分佈並非良策,亦有機會影響本來在該處生長的其他植物

實際上,由人手去栽種自然更新能力低、較為罕有的植物物種,本地有先例
印象中政府曾經在港島做過蘭花遷地保育
最後因為存活率太低,又無成本效益而放棄
固然上面提到既殼斗科/茶科植物作遷地保育的存活率,應該會高過高度依賴fungal mycorrhizal interactions的蘭花
但大規模去做我覺得可行性仍然不高,效果亦遠遠不及用動物去做
作者: Aland    時間: 2017-5-5 03:46



QUOTE:
原帖由 jasonpoon 於 2017-5-5 00:36 發表
another point: it was said many years ago by the then mainly foreign naturalists that the "fung shui" woods at the back of villages are of special interest as they may resemble the "ori ...

To me, feng shui woods are unlikely to be very natural. Although kept a woodland, villagers often plant fruit trees and many economic tree species in them. However, since almost all other lowland forests are gone during years of cultivation and WWII, these little disturbed patches are probably the best we've got.
作者: fai1888    時間: 2017-5-5 09:56



QUOTE:
原帖由 Aland 於 2017-5-5 03:19 發表

實際上,由人手去栽種自然更新能力低、較為罕有的植物物種,本地有先例
印象中政府曾經在港島做過蘭花遷地保育
最後因為存活率太低,又無成本效益而放棄
固然上面提到既殼斗科/茶科植物作遷地保育的存活率,應該會高過高度依賴fungal mycorrhizal interactions的蘭花
但大規模去做我覺得可行性仍然不高,效果亦遠遠不及用動物去做 ...

假設大嶼山的物種的確比其他香地方少很多,我們多種原生植物後,say 20年後,再加上多一些rodents,如松鼠;理論上松鼠應該再不需要靠人類食物,因爲國外松鼠在殼斗科植物的確有很多文獻support.
  以香港氣候,應該多d evergreen board leaf sp. 如殼斗科。大嶼山與大東山上一些能逃過2戰的砍伐與山火小林,應該給我們多一些線索我們原來的物種。風水林與一小塊的劫後餘生(林)應該能夠給我們參考原來面貌。
  既然2戰我們幾乎全部破壞了大部分樹林與相關動物,我們該儘量恢復戰前的面貌。
我自己觀察到香港島好似殼斗科植物比較多而且成林,香港常見的都可以找到,這能不能講系松鼠功勞?之前有research提過松鼠有30-40%還是會以原生植物爲糧食的.
作者: jasonpoon    時間: 2017-5-5 11:26



QUOTE:
原帖由 Aland 於 2017-5-5 03:46 AM 發表

To me, feng shui woods are unlikely to be very natural. Although kept a woodland, villagers often plant fruit trees and many economic tree species in them. However, since almost all other lowland for ...

I lived for some years in a Lantau's village before. the fung shui wood behind indeed has no access path and remain undisturbed (as far as known) for fung shui purpose. the fruit trees are planted in front of the village, mainly 黃皮 & 龍眼, further are some poultry cages and the cultivated fields.
作者: jasonpoon    時間: 2017-5-5 12:09



QUOTE:
原帖由 fai1888 於 2017-5-5 09:56 AM 發表


假設大嶼山的物種的確比其他香地方少很多,我們多種原生植物後,say 20年後,再加上多一些rodents,如松鼠;理論上松鼠應該再不需要靠人類食物,因爲國外松鼠在殼斗科植物的確有很多文獻support.
  以香港氣候,應該多d evergree ...

the fact that the HK Island maybe more similar to the "original" flora & fauna may has several hypotheses:

1. pre-1842 colonial period, hk island being hilly may have relatively little farmers but mainly fishermen settling at boats or near shore. thereby the hilly forests are relatively spared of human influence. the legendary waterfall ex pokfulam area as told by age old fishermen gave out "fragrant" or "sweet" freshwater for fishermen to collect. its been another suggestion for the origin of the name of hong kong.

2. post-1842 colonial period, hk island being the main British settlment would see mainly commercial and residential develoments near shore and up to "mid-levels". this preserved better the flora and fauna in the hills and over the industrialization period. the British used HK mainly as a trading port rather than a factory and the elites and aristocrats build houses in mid-levels thereby further protected the woods around their residence.

3. the kowloon peninsula south of the lion rock should have lost all of the flora or fauna due to settlement, reclamation and later massive immigration. it should originally be a sandy cove and some lowland forests.

4. NT area north of the lion rock should be some shrubland ("thorn-land" was the past name for shatin), extensive lowland forests before major agriculture development. wellknown old settlements may extend about 500 years back. some very old settlements maybe there even around 秦漢 period. the major indigenous 圍村 settlements may also starting from late Song Dynasty.

5. isolated neolithic settlements have been excavated eg. in Lamma Island. these areas though originally rich in megafauna are influenced critically by human early in history. the original flora and fauna may only be inferred from possible lesser developed SE Asian regions or the Subtropical Oriental Region zoogeographically.

6. Concerning the Island of Lantau, it is likely that lowlands are settled and disturbed quite early. consider the nearby 屯門 and 東涌炮台, the place should be critically deforested, cultivated and hunted around the Song period. any major hill fire could also have devastated the hill forests. it may have become mainly a hilly grassland / badland habitat with lowland cultivations around eg. Sha Lo Wan, Tung Chung, Mui Wo and Pui O areas for several hundred years. continuous small scale deforestation was noted as late as in the 1970's by myself. the result maybe the extinction of forest megafauna while lowland herbivores and omnivores ie. Muntiacus reevesi and Sus scrofa remained.

[ 本帖最後由 jasonpoon 於 2017-5-5 16:42 編輯 ]
作者: fai1888    時間: 2017-5-5 13:11



QUOTE:
原帖由 jasonpoon 於 2017-5-5 12:09 發表



the fact that the HK Island maybe more similar to the "original" flora & fauna may has several hypotheses:

1. pre-1842 colonial period, hk island being hilly may have relatively litt ...

As far as I know the forest HK Island is also a secondary forest after the WW2, many early pictures supported that, HK island was a bare hill side. But since HK Island is important in political and economic perspective, on the protection of hill fire and forest rehabitation. It's recovered very well. But how close is that to the original one?
作者: Aland    時間: 2017-5-5 14:47



QUOTE:
原帖由 jasonpoon 於 2017-5-5 11:26 發表


I lived for some years in a Lantau's village before. the fung shui wood behind indeed has no access path and remain undisturbed (as far as known) for fung shui purpose. the fruit trees are planted i ...

You are probably right about villagers mainly planting fruit trees in front instead of behind the village, but as far as I know, villagers also utilize the margins of the Fung Shui woods to plant fruit trees, and I do recall seeing some fruit trees (龍眼、荔枝、烏欖、白欖) in Feng Shui woods.

Apart from fruit trees, I vaguely recall that many villages use Fung Shui woods as a source of timber. That may explain the abundance of certain tree species associated with timber production in Fung Shui woods. An example is  Cinnamomum camphora, the Camphor tree. This species, although listed as a common native, seems to be quite rare in secondary forests and forest further away from village settlements, but populations of very large trees are often found in Fung Shui woods. I suspect villagers plant them deliberately for its high quality timber, and its presence is probably an evidence of human disturbance in Fung Shui woods.

Again, we have to keep in mind that Fung Shui woods being disturbed habitats doesn't undermine the importance of these quite ancient fragments of forests. Many plant and animal species are restricted to Fung Shui woods, and the structure of these fragments are likely are best guess of what the original lowland forests looks like.

Here is a report from a study done by AFCD on plants in Fung Shui woods:
https://www.afcd.gov.hk/english/publications/publications_con/files/hkbonewsletter8.pdf
作者: jasonpoon    時間: 2017-5-5 15:27

"... Cinnamomum camphora, the Camphor tree. This species, although listed as a common native, seems to be quite rare in secondary forests and forest further away from village settlements, but populations of very large trees are often found in Fung Shui woods. I suspect villagers plant them deliberately for its high quality timber, and its presence is probably an evidence of human disturbance in Fung Shui woods."

Can we argue in reverse? C. camphora was indeed very abundant in original lowland forest of HK and indeed S. China. the idea of re-cultivating trees for timber should be rare among early farmers in HK. why they do not plant in open deforested area but instead in their revered Fung Shui woods?

how long does it need to wait for planted camphor trees to grow to good timber size? that physiology of the tree i do not know.    but camphor timber with its characteristic strong smell is good for stoage boxes (樟木櫳) rather than used for furnitures and house building. the demand for camphor in large amount is questionable.

"Again, we have to keep in mind that Fung Shui woods being disturbed habitats doesn't undermine the importance of these quite ancient fragments of forests. Many plant and animal species are restricted to Fung Shui woods, and the structure of these fragments are likely are best guess of what the original lowland forests looks like."

alas, while the floral composition maybe there, the too small size of the forest could not sustain the megafauna which disappeared dispite the final hiding places. if any sessile species may survive and breed in those Fung Shui woods separately, those woods may act as isolating islands and undergone genetic drift and possible speciation... look for evidence in wingless insects and worms maybe...
作者: mathew    時間: 2017-5-5 16:06     標題: 回覆 #32 Aland 的帖子

其實我深受Jurassic Park的概念影響
重新引入herbivore, 大自然會怎樣調整population?
1. 缺乏食物?
會否在飢餓前過度採食 / 人類餵飼令population高於自然承載量 / ...
2. 由carnivore捕食?
現存野外的carnivore能否勝任 / 引入carnivore / ...
3. ......

目前我們真的對環境有足夠認識去引入物種嗎?
不時看到野豬的新聞, 十分懷疑香港能承載更多動物的條件.


回覆 #37 fai1888 的帖子
一直討論原始植被, 原生動物.
請問如何定下界線?
i. 以地厘分布尚有間斷分布的難題;
ii. 若論從前(時間)有某物種, 應以那一標準決定? 討論間有提及宋朝, 1842年前/後, WWII, 何時存活於此地謂原生?
作者: fai1888    時間: 2017-5-5 23:25



QUOTE:
原帖由 mathew 於 2017-5-5 16:06 發表

一直討論原始植被, 原生動物.
請問如何定下界線?
i. 以地厘分布尚有間斷分布的難題;
ii. 若論從前(時間)有某物種, 應以那一標準決定? 討論間有提及宋朝, 1842年前/後, WWII, 何時存活於此地謂原生?

好問題,呢個好深,我自己都有咁唸過,無答案
更正一下,我覺得都起碼WWII前~~

[ 本帖最後由 fai1888 於 2017-5-8 18:01 編輯 ]
作者: Aland    時間: 2017-5-9 09:59



QUOTE:
原帖由 fai1888 於 2017-5-5 09:56 發表


假設大嶼山的物種的確比其他香地方少很多,我們多種原生植物後,say 20年後,再加上多一些rodents,如松鼠;理論上松鼠應該再不需要靠人類食物,因爲國外松鼠在殼斗科植物的確有很多文獻support.
  以香港氣候,應該多d evergree ...

我自己覺得大嶼山就算物種較少,殼斗科/茶科植物的比例其實不比新界低
尤其鳳凰山,基本上到某個高度之後殼斗科/茶科是優勢種
應該不需要靠刻意種植殼斗科植物維持新引入傳種者population

至於殼斗科在港島是否被松鼠有效傳播,我覺得難以單憑感覺下定論

你提到外國研究,確實,絕大部分殼斗科植物都靠scatter-hoarding animals傳播種子
但實際上scatter-hoarding animals亦紛陳多樣,很多地區其實靠雀鳥
要應用在香港身上,還需鄰近地區scatter-hoarding animals的資料
可惜華南地區deforestation嚴重,能保留原貌的地區不多,而研究亦相當缺乏
做一個簡單Google search,最近都要去到秦嶺:
https://www.researchgate.net/publication/257671850_Seed_dispersal_of_three_sympatric_oak_species_by_forest_rodents_in_the_Qinling_Mountains_Central_China

而要留意的是,松鼠絕對並非唯一一種scatter-hoarding mammals, 很多大型鼠類其實亦非常重要
有興趣可以參考http://onlinelibrary.wiley.com/doi/10.1111/1365-2745.12113/abstract
篇文有講油茶用小泡巨鼠傳種,亦有提到不同鼠類可以是seed disperser亦可是seed predator

最後更正一點
二戰前香港其實已經光禿一片
斬薪柴活動,在香港仍是農業主導時已經清除大部分原生樹林
二戰清除的,主要是後來政府所種植的植林
我上文用二戰做分界點,主要是因為二戰是香港最後一次大型deforestation,而非因為戰前香港森林好好景

[ 本帖最後由 Aland 於 2017-5-9 12:12 編輯 ]
作者: Aland    時間: 2017-5-9 12:05



QUOTE:
原帖由 mathew 於 2017-5-5 16:06 發表
其實我深受Jurassic Park的概念影響
重新引入herbivore, 大自然會怎樣調整population?
1. 缺乏食物?
會否在飢餓前過度採食 / 人類餵飼令population高於自然承載量 / ...
2. 由carnivore捕食?
現存野外的carnivore能否勝任 / 引入carnivore / ...
3. ......

有趣的問題......

我自己深信,任何物種都有carrying capacity,就算無明顯predator,population都不會無限增長
上面提到的野豬是一例
野豬在香港基本上無predator,但雖然現時數目可能已經超越以往有華南虎、有豹時的水平,對本地植披仍未至於產生嚴重影響
亦不會引致豬「豬」羅紀公園

事實上超越carrying capacity,乃常有之事
一個正常的動物群族,只要growth rate未算太低,population size都會oscillate and cyclically, or chaotically, go over the carrying capacity
可參考:http://openlandscapes.zalf.de/OpenLandscapesWiki_Glossaries/Aspects%20of%20Ecosystem%20Dynamics.aspx

當然,引入物種帶來生態災難歷史上例子不少(棕樹蛇、紅火蟻)
但一般認為主因是因為外來物種完全無天敵牽制,而parasitic load極低所致
引入毗鄰地區的物種引起生態災難已經鮮有聽聞,重新引入物種就更加少聽會造成負面影響

反觀上面提到的小泡巨鼠、松鼠
很難想象這類果食性的scatter-hoarding species可以引來什麼生態災難
尤其本地predator,例如豹貓、猛禽應該可以取食這些體型不大的rodents?
又,若果仍然擔心這些rodents會造成生態災難,可以先隔離一個patch做實驗,例如用外島(有先例,印象中丫洲就曾經用作測試菟絲子控制薇甘菊)

講真,我認同引入物種有風險
但當一個keystone species對維持一個地區的植披結構,生態系統有深遠影響
而不引入長遠而言會引致三四十種植物,連帶賴以生存的真菌、昆蟲一併消失的時候
我覺得至少要考慮承受有關風險落手去做

QUOTE:
一直討論原始植被, 原生動物.
請問如何定下界線?
i. 以地厘分布尚有間斷分布的難題;
ii. 若論從前(時間)有某物種, 應以那一標準決定? 討論間有提及宋朝, 1842年前/後, WWII, 何時存活於此地謂原生?

個人觀感(上次都有提到):
若一個物種透過自然傳播過程來到香港,該物種應該被視為原生

不過定義歸定義,要確認香港物種當中那些是原生種,幾乎不可能
而這個definition亦有灰色地帶
例如不少農地物種可能是透過天然過程來到香港,但物種在香港能夠立足,全賴人類開墾農地
這情況下又算不算原生?

而最後,將所有物種歸類為原生、非原生,有意義嗎?

[ 本帖最後由 Aland 於 2017-5-9 12:14 編輯 ]
作者: mathew    時間: 2017-5-10 09:54     標題: 回覆 #43 Aland 的帖子



QUOTE:
......

當然,引入物種帶來生態災難歷史上例子不少(棕樹蛇、紅火蟻)
但一般認為主因是因為外來物種完全無天敵牽制,而parasitic load極低所致
引入毗鄰地區的物種引起生態災難已經鮮有聽聞,重新引入物種就更加少聽會造成負面影響

反觀上面提到的小泡巨鼠、松鼠
很難想象這類果食性的scatter-hoarding species可以引來什麼生態災難
尤其本地predator,例如豹貓、猛禽應該可以取食這些體型不大的rodents?
又,若果仍然擔心這些rodents會造成生態災難,可以先隔離一個patch做實驗,例如用外島(有先例,印象中丫洲就曾經用作測試菟絲子控制薇甘菊)

講真,我認同引入物種有風險
但當一個keystone species對維持一個地區的植披結構,生態系統有深遠影響
而不引入長遠而言會引致三四十種植物,連帶賴以生存的真菌、昆蟲一併消失的時候
我覺得至少要考慮承受有關風險落手去做

好奇一問, 可否分享一些 "引入毗鄰地區/重新引入 物種" 的例子, 謝謝.

無論是想像/理論/實驗, 都只是推測, 目前我們有足夠的智識/智慧去作出這決定嗎?
在認知不足時, 我會偏向保守的反應/決定.

始終人類不是管理大自然, 而只是大自然的一部分, 應盡力與大自然共存.

QUOTE:
......

而最後,將所有物種歸類為原生、非原生,有意義嗎?

這要視乎在那一角度討論. 這討論最初正正在說赤腹松鼠為引入種, 沒有原生何來引入.

很務實的說, 若外來物種能找到其niche, 與其他物種有合理互動, 有何可議?
只是在主動引入的時候, 無論出發點為何, 應該萬分謹慎.
作者: jasonpoon    時間: 2017-5-10 15:46



QUOTE:
原帖由 mathew 於 2017-5-10 09:54 AM 發表
好奇一問, 可否分享一些 "引入毗鄰地區/重新引入 物種" 的例子, 謝謝.

無論是想像/理論/實驗, 都只是推測, 目前我們有足夠的智識/智慧去作出這決定嗎?
在認知不足時, 我會偏向保守的反應/決定.

始終人 ...

Gambusia affinis (食蚊魚), the mosquito fish originally inhabiting Central America/Mexico was introducted to control mosqitoes in HK and many parts of the world after WWII. As for HK, this should be a long-range but not adjacent region introduction. It was quite well established once in the 1950's - 80's (personal hearsay & observation). It has since become rare perhaps following the decline of local farming activities. They frequent the field-side ditches, water pools for irrigation, etc. Cessation of farming has reduced the water quantity and quality in the ditches and possible overgrowth of weeds & water plants rendered their habitat less suitable for their existence. Increasing spraying of mosquito oil by the govt and pollution may also suffocated a lot of them. Being adapted to more stagnant water, they may not be able to establish themselves in fast flowing cleaner streams in HK. Competitive decline due to local mid-water species may also contribute.

Tilapia (or Oreochromis) mossambicus/niloticus/zillii species group & hybrids (金山鯽, 羅非魚, 福壽魚) was probably introduced into HK as early as in the 1940's, possibly from Indonesia or Africa directly. Until today, they are widely established in local reservoirs, muddy or sandy rivers, brackish waters and mangroves. Hybrids in culture and in the wild are highly possible contributing to increased adaptability especially to cold winter temperature. Massive deaths in winter due to cold front were seen as late as in 70's and 80's but fewer later on possible due to adaptation and global warming. They are omnivorous and probably preyed on bottom dwelling original fishes and invertebrates.

Xiphophorus helleri & spp. (青劍, 紅劍, 月魚, 鴛鴦) & Poecilia spp. (孔雀, 摩利) have been found in local streams increasingly probably from 1990's likely due to release from aquarium hobbyists. They are confirmed to have established breeding populations in reservoir catchments and local streams and ditches such as Tung Chung River. Being mid water fast moving omnivores originating around Middle  & South America, they may compete with common local species such as Barbodes semifasciolatus and Parazacco spilurus. However, lowland streams in HK are already fully and extensively human disturbed in many other aspects. The decline or disappearance of Barbodes semifasciolatus, Pseudoastromyzon sp. locally may be a result of their introduction and competition.

Various larger introduced aquarium fishes maybe fished or caught in reservoirs or catchments. I personally have known Chitala ornata (東洋刀) (Thailand & SE Asia), Pseudoplatystoma fasciatum (鴨嘴鯰) (S. America), Loricaria spp. (琵琶) (S. America). Some species of Channa (生魚, 鱧) may not be natural to HK.

Even one onshore seawater species is definitely introduced, the Red Drum (星鱸) (Sciaenops ocellatus) was originated from N. American East Coast and is a worldwide seawater aquaculture species.
作者: jasonpoon    時間: 2017-5-10 17:55

以上其實只有食蚊魚係當局有心引入到野外的, 可能最初係想佢地係D靜水池塘繁育控制孑孓. 可惜那些水體有其他污染搞到魚兒都頂唔順

其他都唔算係有計劃的引入到野外...
作者: jasonpoon    時間: 2017-5-11 05:07

經典的國際例子, 可參考:

1. 中國長江下游的四不像 (麋鹿) Elaphurus davidianus
https://zh.wikipedia.org/wiki/%E9%BA%8B%E9%B9%BF

2. 美國黃石國家公園的狼 Canis lupus
https://en.wikipedia.org/wiki/Hi ... lowstone#Subspecies
作者: Aland    時間: 2017-5-13 14:40



QUOTE:
原帖由 mathew 於 2017-5-10 09:54 發表
好奇一問, 可否分享一些 "引入毗鄰地區/重新引入 物種" 的例子, 謝謝.

無論是想像/理論/實驗, 都只是推測, 目前我們有足夠的智識/智慧去作出這決定嗎?
在認知不足時, 我會偏向保守的反應/決定.

始終人類不是管理大自然, 而只是大自然的一部分, 應盡力與大自然共存.

這要視乎在那一角度討論. 這討論最初正正在說赤腹松鼠為引入種, 沒有原生何來引入.

很務實的說, 若外來物種能找到其niche, 與其他物種有合理互動, 有何可議?
只是在主動引入的時候, 無論出發點為何, 應該萬分謹慎.

關於重新引入曾經出現過的keystone species,或其ecological equivalent,可以參考wikipedia "rewilding" 一頁
https://en.wikipedia.org/wiki/Rewilding_(conservation_biology)

實際上,此概念近幾年在歐美各國相當流行,有牛有鹿有熊有狼有馬,非常多樣化
其中一個經典例子為Oostvaardersplassen,當地政府非常大規模地重新引入物種,minimize management,以嘗試恢復昔日光景,並取得一定成果
http://www.wildeurope.org/index.php/restoration/national-strategies/rewilding-holland

當然過程中確實會引起爭議,尤其重新引入top predator
例如在Scotland重新引入消失了350年的狼,就在英國國內引起不少討論
(可參考:http://www.bbc.co.uk/news/magazine-33017511

反觀香港
我個人認為,可以與大自然共存當然最理想
但過去幾百年來人類對本地生態的干預太徹底,以不造成額外影響為由去抗拒active management/rewilding已經未必適切
上面有提到,香港的樹林很可能有非常龐大的extinction debt
以往deforestation/megafaunal extinctions所造成的影響,可能較想象中龐大,只是未曾完全彰顯出來而已
要去減少過去人類對本地系統所造成的破壞,需要active management
而重新引入一些小型的scatter-hoarding rodents,其實已經是風險較低,成本效益較高的選項

至於原生和引入種的問題
同意出發點其實是引入種究竟有否與環境產生合理互動(值得再討論的是,何謂“合理互動”?)
我相信無人會否定薇甘菊/福壽螺等物種,對本地生態平衡造成負面影響
但像蒲桃這類似乎相當融入本地生境的引入種,在保育過程中如何定位?
再極端少少,如上面所述,本地不少農地物種,例如各種蓼,其實有可能本質是若干年前的外來種
如是者,又是否值得再去尋根究底,一一分類?
作者: Aland    時間: 2017-5-13 15:18



QUOTE:
原帖由 jasonpoon 於 2017-5-5 15:27 發表
Can we argue in reverse? C. camphora was indeed very abundant in original lowland forest of HK and indeed S. China. the idea of re-cultivating trees for timber should be rare among early farmers in HK. why they do not plant in open deforested area but instead in their revered Fung Shui woods?

That is not impossible. If that is indeed the case, the question we should be asking ourselves is why is C. camphora so scarce in secondary lowland forests? Why is the regenerative ability of the species so low nowadays? Is it facing the same problem Fagaceae is facing currently, or is the regenerative ability affected by other factors such as pests and diseases? (galls on fruits of Cinnamomum spp. affecting fruit formation maybe?)

Returning to my hypothesis of camphor trees being deliberately planted in Fung Shui woods, I could see reasons why villagers might prefer planting camphor trees in Fung Shui woods of all places. To start with, Fung Shui woods are easily accessible. It is not preferable if a 樟木櫳 sized piece of timber has to be transported from far away back to the village. Also, if we refer back to the photos taken in that era, the hillslopes in large parts of Hong Kong are bare and deforested. These slopes are likely to be depleted of nutrients and very exposed to wind. Not suitable for plantation in a small scale. As you said, the demand for 樟木櫳 isn't that large. It is simply not worth it to create a whole plantation of camphor trees. Planting a few trees near the village might be more sensible for the villagers.

I think asking some old villagers might yield some answers.

QUOTE:
alas, while the floral composition maybe there, the too small size of the forest could not sustain the megafauna which disappeared dispite the final hiding places. if any sessile species may survive and breed in those Fung Shui woods separately, those woods may act as isolating islands and undergone genetic drift and possible speciation... look for evidence in wingless insects and worms maybe...

I agree that Fung Shui woods are unlikely to sustain large animals, but I think at least some insects should persist. While many birds, butterflies, and mammals disappeared, I vaguely remember that Hong Kong has a surprisingly high diversity of ant species. Likely a relic of the high diversity subtropical rainforests we once had.

To be honest, I don't think genetic drift and natural selection would be sufficient to result in speciation events among different Fung Shui woods. You need quite almost complete reproductive isolation to prevent the swamping effect as a result of gene flow. Personally, I believe that populations between different Fung Shui woods would definitely be less reproductively isolated than populations on small islands. Maybe we should start with finding new sessile species in Ninepin group?


Actually, I would quite like to know when did Fung Shui woods start to become isolated patches of forests? Or more generally, when did large scale deforestation in Hong Kong occur? According to Flora of Hong Kong (I think it's volume 2?), even the earliest travelers from Britain described Hong Kong as a bare island with no forest cover. So the deforestation must have occurred before that. Do we ever get records from 明清 about vegetative cover in Hong Kong?
作者: jasonpoon    時間: 2017-5-14 16:19



QUOTE:
原帖由 Aland 於 2017-5-13 03:18 PM 發表

That is not impossible. If that is indeed the case, the question we should be asking ourselves is why is C. camphora  so scarce in secondary lowland forests? Why is the regenerative ability of the sp ...

Just another recent reading indicated that the planting of Aquilaria sinensis (土沉香) for incense (線香) making in HK (indeed the NT) was once a major economic produce that may even account for the name of 香港. That trade is likely to date back to around the Song Dynasty as ship sailing has to be advanced enough for sea trade.

A. sinensis could well be a key lowland tree species in "original" HK and indeed S. China lowland forests as it is endemic to S. China. If this craft of incense making is widespread once in NT villages, and if the logic of near Fung Shui wood cultivation is true, then we would expect remnants of old planted A. sinensis around Fung Shui woods. Is it the case?

As A. sinensis trees have been hunted badly, could a widespread plantation of this species (if botanically feasible) be done in HK?

[ 本帖最後由 jasonpoon 於 2017-5-14 19:01 編輯 ]
作者: jasonpoon    時間: 2017-5-15 22:33

QUOTE
"I agree that Fung Shui woods are unlikely to sustain large animals, but I think at least some insects should persist. While many birds, butterflies, and mammals disappeared, I vaguely remember that Hong Kong has a surprisingly high diversity of ant species. Likely a relic of the high diversity subtropical rainforests we once had.

To be honest, I don't think genetic drift and natural selection would be sufficient to result in speciation events among different Fung Shui woods. You need quite almost complete reproductive isolation to prevent the swamping effect as a result of gene flow. Personally, I believe that populations between different Fung Shui woods would definitely be less reproductively isolated than populations on small islands. Maybe we should start with finding new sessile species in Ninepin group?

Actually, I would quite like to know when did Fung Shui woods start to become isolated patches of forests? Or more generally, when did large scale deforestation in Hong Kong occur? According to Flora of Hong Kong (I think it's volume 2?), even the earliest travelers from Britain described Hong Kong as a bare island with no forest cover. So the deforestation must have occurred before that. Do we ever get records from 明清 about vegetative cover in Hong Kong?"
END QUOTE


I once thought about the effect of typhoon in S. China on dispersal and genetic remixing of species especially for freshwater fishes which are easily isolated especially in hillstreams. Isolating mechanisms maybe alleviated by the frequent blown out individuals of small sizes.

Sources reported that early British colonists described HK as a "barren rock". However, I think this might be an overstatement as I doubt any Englishman had actually walked or charted the inland of NT. Systematic surveying of lands in NT only begin after the 1898 Convention and was done mainly by indian surveyors. There were history of early resistances from villagers silenced only by cannon blows from British warships. Throughout early to mid 20th century, urbanization happened mainly in HK Island and Kowloon areas. It is also a matter of question about the extend of deforestation during WWII. Major influx of people from China occurred in around 1949 and 1967. While the country parks were started around 1977.
作者: mathew    時間: 2017-5-16 19:56     標題: 回覆 #50 jasonpoon 的帖子



QUOTE:
Just another recent reading...

這類土沉香的文章, 要小心閱讀.
要好好判斷所考證的歷史資料可信性.
作者: jasonpoon    時間: 2017-5-16 22:10



QUOTE:
原帖由 mathew 於 2017-5-16 07:56 PM 發表

這類土沉香的文章, 要小心閱讀.
要好好判斷所考證的歷史資料可信性.

Thanks indeed mathew. Everyone should exercise rationality and objectivity in science or life. Do you know of any evidence or report that indicate another story? Given the fact that controlling poaching is nearly impossible in the long run, the fate of the few surviving A. sinensis in the wild seems doomed.

In case it is possible to cultivate or investigate possible methods of propagation of the species in for eg. government nurseries, then this would be a concrete first step for preservation of the species.

The ecology of Aquilaria spp. in SE Asia points out that these species like to grow around mangroves or wetlands. Perhaps the lost of wetlands have contributed to their decline and rareness. It seems sadly that A. sinensis is more suitable for use as chinese herb or incense probably due to its higher sap content.

[ 本帖最後由 jasonpoon 於 2017-5-16 22:11 編輯 ]
作者: Aland    時間: 2017-5-19 07:29



QUOTE:
原帖由 jasonpoon 於 2017-5-14 16:19 發表



Just another recent reading indicated that the planting of Aquilaria sinensis (土沉香) for incense (線香) making in HK (indeed the NT) was once a major economic produce that may even account for th ...

Indeed Aquilaria sinensis is quite common in lowland forests and Feng Shui Woods. However, I have also read that most of the original plantations were destroyed with incense unsustainably exploited by villagers during 遷界令 in the Qing Dynasty, when almost all villages in Hong Kong were deserted. If this is true, then I suppose what we see nowadays is the progeny of the very few remaining trees after the 遷界令.

Also, unlike camphor trees, A. sinensis seems to be regenerating pretty successfully in lowland forests. Treelets of incense trees are pretty common despite being targeted by illegal poachers. This could be attributed to two factors: its shade tolerance, mentioned above; and the fact that its dispersal agent, large wasps such as 印度側異腹胡蜂 (Parapolybia indica indica), are still abundant and effective in dispersing the seeds. Therefore, I think it is unlikely that incense trees would be completely wiped out under poaching, which only targets large to medium trees. However, poaching is definitely causing a large drop in the population size of incense trees, and I agree that actively planting trees could be a way out in this case.

For your reference, I have witnessed wasps trying to remove the seeds of incense trees (see #63): http://www.hkwildlife.net/Forum/redirect.php?tid=5953&goto=lastpost#lastpost
The research paper in #63 looked into how chemical cues produced by the incense tree tricks the wasp into believing that the seed is an insect.
作者: Aland    時間: 2017-5-19 09:13



QUOTE:
原帖由 jasonpoon 於 2017-5-15 22:33 發表
I once thought about the effect of typhoon in S. China on dispersal and genetic remixing of species especially for freshwater fishes which are easily isolated especially in hillstreams. Isolating mechanisms maybe alleviated by the frequent blown out individuals of small sizes.

Typhoons might be important in genetic remixing. However, I suppose that is more relevant to insects, plants, and birds? It is hard to imagine fish being blown off from one stream to another. I actually think that freshwater fish, especially primary freshwater fish that never leaves the river basin it is in, are quite genetically isolated. There has been quite a lot of examples of impressive adaptive radiation and the evolution into different morphs in some freshwater fish taxa. Examples include the three-spine sticklebacks in North America showing high regional variation, guppies in Trinadad with different morphs below and above the waterfalls, and the amazing cichlids in Lake Victory and Lake Malawi. Even if there is gene mixing between populations, I believe birds carrying fish around and human activity might actually be a more plausible explanation? I wonder if anyone looked into the Fst values of primary freshwater fish in Hong Kong?

QUOTE:
Sources reported that early British colonists described HK as a "barren rock". However, I think this might be an overstatement as I doubt any Englishman had actually walked or charted the inland of NT. Systematic surveying of lands in NT only begin after the 1898 Convention and was done mainly by indian surveyors. There were history of early resistances from villagers silenced only by cannon blows from British warships. Throughout early to mid 20th century, urbanization happened mainly in HK Island and Kowloon areas. It is also a matter of question about the extend of deforestation during WWII. Major influx of people from China occurred in around 1949 and 1967. While the country parks were started around 1977.

http://twpcentre.weshare.hk/oceandeep3000/articles/756909

Photos of new territories from 1950 clearly shows hillslopes in New Territories are quite bare with only short vegetation, and the slopes that are actually forested are mainly covered with sparse pine trees. Clearly not the broadleaved subtropical rainforest one would expect in the absence of heavy human disturbance. At that time, the economy of New Territories was still heavily agricultural, and the deforestation is probably caused by villagers going uphill to collect fuelwood or directly using the slopes for 梯田 as some of the photos show. In fact agricultural activity in the New Territories could be dated back to settlements in Ho Chung Valley 4000 years ago. Evidence suggested that people in the Late Neolithic Period already started planting rice in the valley. Hence, vegetative change by agriculture in New Territories must have occurred very very long time ago. The main question is, how severe was it? When did most of our forests disappear?

I found a very detailed government account of changes in landscape in Hong Kong that may give us some answers:
http://www.pland.gov.hk/pland_en/p_study/prog_s/landscape/tech_report/ch5.htm

The basic idea is that, settlements from Neolithic period till 遷界令 in Qing Dynasty were only focused in flood plains and coastal areas. Agriculture, salt industry, and lime industry came into play in different times during this period. These industries, especially the lime industry, needs quite a lot of fuel wood from hillslopes. The resulting deforestation was gradual but substantial, with pollen data showing the dominance of grasses and the decline of pine trees/Fagaceae after the settlements are established. (The fact that other large tree families such as Lauraceae 樟科 is not represented in pollen data does not indicate that pine forests are dominant. It is probably because these families are insect pollinated and leave only a faint pollen record). The end of the 遷界令 in 1669 seems to be a very important point in the vegetative history in Hong Kong. In addition to the return of the people who left Hong Kong during the 遷界令, Hakka people moved into Hong Kong and created new settlements. Hakka people converted slopes to 梯田 and occupied even hilly areas.

Based on the information provided, I speculate that megafauna such as elephants and rhinos probably went locally extinct one by one since the Neolithic period. Gradual deforestation to provide fuel wood for salt and lime industries wiped out large animals dependent on large patches of forests, with Hakka settlements on mountains giving them a final hit. Finally, other more resilient predators such as tigers and foxes went locally extinct when rural population surged once again under British rule, with habitats heavily fragmented by roads and railways. Urbanization might actually be beneficial to preserving forests since people living in cities are no longer involved in agricultural activity, and does not have to depend on trees on hillslopes for fuel wood.

The main message is, the ecosystem in Hong Kong is degraded very early in history.
作者: jasonpoon    時間: 2017-5-22 17:15

"Typhoons might be important in genetic remixing. However, I suppose that is more relevant to insects, plants, and birds? It is hard to imagine fish being blown off from one stream to another. I actually think that freshwater fish, especially primary freshwater fish that never leaves the river basin it is in, are quite genetically isolated. There has been quite a lot of examples of impressive adaptive radiation and the evolution into different morphs in some freshwater fish taxa. Examples include the three-spine sticklebacks in North America showing high regional variation, guppies in Trinadad with different morphs below and above the waterfalls, and the amazing cichlids in Lake Victory and Lake Malawi."

I must point out that the hypothesis has to find supports in Typhoon and Hurricane Belts of the world, amongst other factors. The occurance of geographically close varieties or subspecies in areas not affected by that level of wind disturbance is evolutionarily predicted. Adaptive radiation in African Rift Lake Cichlids depends on occurance of micro habitats within the lakes - that are relatively stable and not disturbed on large scale.

Possible wind dispersal for large animals such as snails and lizards are not uncommon in studies around the Caribbeans and East Atlantic Islands. Individuals need not be mature and could be smaller juveniles to be carried by typhoon scale wind. I think of variations and species of fishes in highly isolated primary freshwater environment eg. high reach of valleyed hillstreams...
作者: Aland    時間: 2017-5-23 18:42



QUOTE:
原帖由 jasonpoon 於 2017-5-22 17:15 發表
I must point out that the hypothesis has to find supports in Typhoon and Hurricane Belts of the world, amongst other factors. The occurance of geographically close varieties or subspecies in areas not affected by that level of wind disturbance is evolutionarily predicted. Adaptive radiation in African Rift Lake Cichlids depends on occurance of micro habitats within the lakes - that are relatively stable and not disturbed on large scale.

Possible wind dispersal for large animals such as snails and lizards are not uncommon in studies around the Caribbeans and East Atlantic Islands. Individuals need not be mature and could be smaller juveniles to be carried by typhoon scale wind. I think of variations and species of fishes in highly isolated primary freshwater environment eg. high reach of valleyed hillstreams...

Do you have any research papers related to how typhoons could disperse relatively larger animals such as lizards and snails? I have definitely hear about spiders and insects being dispersed by wind, but not much about snails and lizards.
作者: jasonpoon    時間: 2017-5-23 21:49

General discussions on wind dispersal maybe searched in www.


For lizards/geckos, the following papers could be found:
Censky, Ellen J.; Hodge, Karim; Dudley, Judy (1998), Over-water dispersal of lizards due to hurricanes, Nature, 395: 556, doi:10.1038/26886

https://www.infona.pl/resource/b ... 8-8aed-d557f2360c79


For snails, the wiki reference is:
https://en.wikipedia.org/wiki/Orthalicus_reses


In general, there was a "Intermediate Disturbance Hypothesis" which theorized upon related issues of diversity and disturbance.

[ 本帖最後由 jasonpoon 於 2017-5-23 22:06 編輯 ]
作者: Aland    時間: 2017-5-23 23:21



QUOTE:
原帖由 jasonpoon 於 2017-5-23 21:49 發表
General discussions on wind dispersal maybe searched in www.


For lizards/geckos, the following papers could be found:
Censky, Ellen J.; Hodge, Karim; Dudley, Judy (1998), Over-water dispersal of liz ...

Thanks for the articles. Interesting read.

On thing to clarify. I think what the articles are suggesting is that bits of forests/trees/logs are being washed off during hurricanes and eventually made their way to new islands instead of animals being 'blown off by the wind' as mentioned above. This sounds more reasonable. In fact, phylogenetic evidence suggests that these 'rafts' moved animals around quite frequently in a long enough time span. Even longer distance oceanic dispersal from Madagascar to India has been suggested for chameleons based on mt-DNA phylogeny of the taxa (http://www.nature.com/nature/journal/v415/n6873/full/415784a.html). An even more bazaar example is  the New World monkeys. Fossil evidence and DNA phylogenetic reconstructions have suggested that all monkeys living in South America are derived from an African common ancestor, and the separation between Old World and New World monkeys are long after the separation of the two continents. Hence, there must have existed a 'raft' made from a patch of forest or floating vegetation large enough to carry a population of monkeys across the Atlantic. It is a contentious idea, but till this date it is still the preferred theory explaining how the New World monkeys got to where they are now. (http://www.bbc.com/earth/story/20160126-the-monkeys-that-sailed-across-the-atlantic-to-south-america).

However, I personally still have doubts about using hurricanes, bad weather, and rafts to explain animal dispersal. In particular, I still believe that it is highly unlikely for freshwater fish to be transferred from one place to another by these mechanisms. Snails, lizards, and monkeys hanging on to tree branches in rafts blown across the ocean, I could imagine, but fish seems unlikely to make it through in this manner..............

QUOTE:
In general, there was a "Intermediate Disturbance Hypothesis" which theorized upon related issues of diversity and disturbance.

The intermediate disturbance hypothesis is a completely unrelated concept I think?

To my understanding, the intermediate disturbance hypothesis suggests that biodiversity in a habitat is highest when disturbance is intermediate. This is based on the assumption that habitats will be increasingly be occupied by a few specialist species highly adapted to the environment if the disturbance is low, and that few species are able to cope under the change and environmental pressures brought about by disturbance if the disturbance is high, both leading to low diversity.

Personally, I am a believer of the intermediate disturbance hypothesis, though I think it is extremely difficult to quantify and prove its existence. This will eventually bring us back to the earlier discussion of whether human intervention/disturbance should be applied to the ecosystem in order to prevent the system from reaching its last succession state, which has relatively low biodiversity. (e.g. should we clear forests to maintain grasslands)

[ 本帖最後由 Aland 於 2017-5-23 23:31 編輯 ]
作者: jasonpoon    時間: 2017-5-24 01:45

"On thing to clarify. I think what the articles are suggesting is that bits of forests/trees/logs are being washed off during hurricanes and eventually made their way to new islands instead of animals being 'blown off by the wind' as mentioned above. This sounds more reasonable."


Longer range "blown off" should be much more likely to be successful when some "rafts" are involved which increase the lift and protect the animal inside. But in shorter range other possibilities become more likely and also consider that typhoon and flooding being a frequent and violent disturbance that would cause mixing of populations. In particular I was thinking if there exist a clear boundary of the range (and genetic distance) of Macropodus hongkongensis and M. concolor, both extends from South China to Hainan Island and (North) Vietnam.


"In fact, phylogenetic evidence suggests that these 'rafts' moved animals around quite frequently in a long enough time span. Even longer distance oceanic dispersal from Madagascar to India has been suggested for chameleons based on mt-DNA phylogeny of the taxa (http://www.nature.com/nature/jou ... full/415784a.html). An even more bazaar example is  the New World monkeys. Fossil evidence and DNA phylogenetic reconstructions have suggested that all monkeys living in South America are derived from an African common ancestor, and the separation between Old World and New World monkeys are long after the separation of the two continents. Hence, there must have existed a 'raft' made from a patch of forest or floating vegetation large enough to carry a population of monkeys across the Atlantic. It is a contentious idea, but till this date it is still the preferred theory explaining how the New World monkeys got to where they are now. (http://www.bbc.com/earth/story/2 ... -to-south-america).


Chameleons are likely originated from Africa and radiated to Europe and Madagascar while later extirpated in Africa. The Atlantic was not that wide in Oligocene and possibly oceanic islands existed between Madagascar and India as suggested by later studies.

Hominids as well as monkeys should have originated both in Africa and migrated to the New World from several possible routes.


"However, I personally still have doubts about using hurricanes, bad weather, and rafts to explain animal dispersal. In particular, I still believe that it is highly unlikely for freshwater fish to be transferred from one place to another by these mechanisms. Snails, lizards, and monkeys hanging on to tree branches in rafts blown across the ocean, I could imagine, but fish seems unlikely to make it through in this manner.............."


How about a gradual "spreading" of some individuals from time to time with ongoing genetic mixing? This should have somehow reduced the diversity index...


"QUOTE:
In general, there was a "Intermediate Disturbance Hypothesis" which theorized upon related issues of diversity and disturbance.

The intermediate disturbance hypothesis is a completely unrelated concept I think?

To my understanding, the intermediate disturbance hypothesis suggests that biodiversity in a habitat is highest when disturbance is intermediate. This is based on the assumption that habitats will be increasingly be occupied by a few specialist species highly adapted to the environment if the disturbance is low, and that few species are able to cope under the change and environmental pressures brought about by disturbance if the disturbance is high, both leading to low diversity.

Personally, I am a believer of the intermediate disturbance hypothesis, though I think it is extremely difficult to quantify and prove its existence. This will eventually bring us back to the earlier discussion of whether human intervention/disturbance should be applied to the ecosystem in order to prevent the system from reaching its last succession state, which has relatively low biodiversity. (e.g. should we clear forests to maintain grasslands)"


It may hardly be a strict one as a common phenomenon of biologic theories and many of its ingredients may be interpreted differently. Be it typhoon or human disturbance or something else, we should be having a low biodiversity in HK. Going back to the topic of 松鼠, if we take that the present populations ex-Lantau were introduced and that food trees for the species are lacking in Lantau, I incline not to consider bringing them to the island in the meantime.

[ 本帖最後由 jasonpoon 於 2017-5-24 04:46 編輯 ]
作者: mathew    時間: 2017-5-25 22:43

似有關, 又似無關...

不該存在的綠色大蜥蜴:對外來種「欲除之而後快」的反思
https://www.thenewslens.com/article/69170
作者: jasonpoon    時間: 2017-5-26 13:06



QUOTE:
原帖由 mathew 於 2017-5-25 10:43 PM 發表
似有關, 又似無關...0

不該存在的綠色大蜥蜴:對外來種「欲除之而後快」的反思
https://www.thenewslens.com/article/69170

我又說魚了...

太平洋的蓑衣鮋 (Lionfish) Pterois spp. 最近幾年在美洲東岸及加勒比海一帶成為嚴重外來種問題. 有地方甚至推廣各色各樣蓑衣鮋菜式鼓勵捕獵食用... 再前時, 鰱魚 (Silver Carp) Hypophthalmichthys molitrix 在美國的侵入(喜跳躍的品系) 亦有不少新聞. 想一下, 在發達國家有人報導的入侵事件, 很可能只是冰山一角. 那些較不顯眼的, 例如香港溪流的青劍, 又會有多少人深入研究?
作者: Aland    時間: 2017-6-4 08:31



QUOTE:
原帖由 mathew 於 2017-5-25 22:43 發表
似有關, 又似無關...

不該存在的綠色大蜥蜴:對外來種「欲除之而後快」的反思
https://www.thenewslens.com/article/69170

講真,撇開動物保育和感情因素,外來種如果成功建立起群族,基本上無論如何控制都難以完全清除
體形較大、族群較小的物種,例如鹿,尚可用捕獵方式控制其群族甚至完全將之清除
但講到植物、魚、昆蟲,成功移除的機會接近零
香港多年來用人手控制薇甘菊,最多只可以稍微減慢其散播,或確保個別比較敏感的地區免受薇甘菊影響(例如鴉洲)
有時見近郊荒田薇甘菊大片生長,實在相當無奈
作者: Aland    時間: 2017-6-4 08:39



QUOTE:
原帖由 jasonpoon 於 2017-5-26 13:06 發表



我又說魚了...

太平洋的蓑衣鮋 (Lionfish) Pterois spp. 最近幾年在美洲東岸及加勒比海一帶成為嚴重外來種問題. 有地方甚至推廣各色各樣蓑衣鮋菜式鼓勵捕獵食用... 再前時, 鰱魚 (Silver Carp) H ...

講到魚,我仍然覺得Lake Victoria的Nile Perch最經典
引入一種魚,不但影響湖中其他魚類,更因為食用Nile Perch要煙熏處理,需要大量木材作燃料,而令附近林木受到毀滅性衝擊
實在誇張

而如我上面所講,其實見到引入種,米已成炊,好多是控制已經太遲而且不太符合成本效益
從源頭著手,減少放生、控制園藝物種/泥土貿易、控制ballast water,比較實際
作者: jasonpoon    時間: 2017-6-8 07:22



QUOTE:
原帖由 Aland 於 2017-6-4 08:39 AM 發表

講到魚,我仍然覺得Lake Victoria的Nile Perch最經典
引入一種魚,不但影響湖中其他魚類,更因為食用Nile Perch要煙熏處理,需要大量木材作燃料,而令附近林木受到毀滅性衝擊
實在誇張

而如我上面所講,其實見到引入種,米已成炊 ...

Thanks for mentioning this classic example. The smoking treatment is unknown to me hope it under control. Some nile perchs can reach human size so smoking would need hell lots of wood.
作者: Aland    時間: 2017-6-8 11:15

再重看本版討論,關於土沉香

QUOTE:
原帖由 jasonpoon 於 2017-5-16 22:10 發表
The ecology of Aquilaria spp. in SE Asia points out that these species like to grow around mangroves or wetlands. Perhaps the lost of wetlands have contributed to their decline and rareness. It seems sadly that A. sinensis is more suitable for use as chinese herb or incense probably due to its higher sap content.

對於資料顯示土沉香長於紅樹林及濕地,我有保留
有無機會可以參考原文?

感覺上長於紅樹林的土沉香是另一種?
因為香港其中一種真紅樹,海漆Excoecaria agallocha,亦被稱為土沉香
作者: Aland    時間: 2017-6-8 11:19



QUOTE:
原帖由 jasonpoon 於 2017-6-8 07:22 發表




Thanks for mentioning this classic example. The smoking treatment is unknown to me hope it under control. Some nile perchs can reach human size so smoking would need hell lots of wood.

It was a shock when I heard about it as well. Apparently this deforestation caused by Nile Perch has many further knock on effects. One of which is that it increased erosion in areas surrounding Lake Victoria and increased lake turbidity. This caused a further hit on the cichlids, which depended on clarity of water for mate recognition. It's just......impressive.....and at the same time horrific.
作者: jasonpoon    時間: 2017-6-10 20:49



QUOTE:
原帖由 Aland 於 2017-6-8 11:15 AM 發表
再重看本版討論,關於土沉香

對於資料顯示土沉香長於紅樹林及濕地,我有保留
有無機會可以參考原文?

感覺上長於紅樹林的土沉香是另一種?
因為香港其中一種真紅樹,海漆Excoecaria agallocha,亦被稱為土沉香 ...

引自維基中文"土沈香":

"台湾亦出产可衍生沉香木质的牙香树。台湾原生种被IUCN物种保育等级评估为接近威胁,分布于西南沿海湿地地区,为耐盐的红树林伴生植物,多数生长于沿海和沼泽地区,这些地方易受开发破坏,许多栖地已划入垦丁国家公园和台江国家公园等及中华民国的国家重要湿地保护中。[2][3][4]此外,亚洲热带、澳洲、波利尼西亚等地区也有牙香树分布。"
作者: mathew    時間: 2017-6-11 18:11     標題: 回覆 #68 jasonpoon 的帖子

維基
參考[4]的連結所指的土沉香正是「海漆」

QUOTE:
土沉香 Excoecaria agallocha L.
科名:大戟科
俗名:山賊仔、水賊、海漆、水漆
保育等級:臺灣原生種,IUCN物種保育等級評估為接近威脅。

http://np.cpami.gov.tw/youth/ind ... 27-16&Itemid=34
作者: jasonpoon    時間: 2017-6-11 18:29



QUOTE:
原帖由 mathew 於 2017-6-11 06:11 PM 發表
維基
參考的連結所指的土沉香正是「海漆」

http://np.cpami.gov.tw/youth/ind ... 27-16&Itemid=34 ...

有點亂了... 那麼應該指出在香港瀕危的"土沉香"是 Aquilaria sinensis. 應該不是紅樹林的植物, 是屬亞熱帶闊葉林.
作者: Aland    時間: 2017-6-13 08:13



QUOTE:
原帖由 jasonpoon 於 2017-6-11 18:29 發表



有點亂了... 那麼應該指出在香港瀕危的"土沉香"是 Aquilaria sinensis. 應該不是紅樹林的植物, 是屬亞熱帶闊葉林.

基本上市面上的沈香應該是Aquilaria sp., 但未必一定是A. sinensis

至於海漆在台灣被稱為土沈香,我其實覺得有少少奇怪
理論上如果海漆被用作沈香代替品,叫土沈香無可厚非,部分台灣網頁亦寫明可燃燒作香
但海漆本身汁液有毒,皮膚接觸後會敏感,入眼可致盲
海漆英文名Blind-your-eye,可見毒性相當
真係會做沈香代替品?抑或祗屬誤傳?
作者: mathew    時間: 2017-6-14 14:49     標題: 回覆 #71 Aland 的帖子

市面上的沉香實在難以說是何品種

過去在香港遇到的 Aquilaria sinensis 均未有結香情況
十分懷疑"土沉香 / Aquilaria sinensis" 應為贗品或替代品, 估計跟 Aquilaria malaccensis 在功效或品質上有分別.
否則何以會用"土"字為名.

而大肆偷伐的原因有可能是以 Aquilaria sinensis 木材加工作 Aquilaria malaccensis 售賣

至於海漆毒性, 會否只限在樹液時才會有效
在燃燒後則消除毒性?
作者: jasonpoon    時間: 2017-6-15 00:04



QUOTE:
原帖由 mathew 於 2017-6-14 02:49 PM 發表
市面上的沉香實在難以說是何品種

過去在香港遇到的 Aquilaria sinensis 均未有結香情況
十分懷疑"土沉香 / Aquilaria sinensis" 應為贗品或替代品, 估計跟 Aquilaria malaccensis 在功效或品質上有分別.
...

想搞清楚一些論點:
1. 當初提起土沉香是討論其可能與香港的風水林的關係, 而根據此網站舊帖及其他資料理解, 香港的土沉香應該是 Aquilaria sinensis. 因其本身不常見及近年偷伐而瀕危. A. sinensis 是華南種分布於廣東至廣西沿岸.
2. 有資料表示其有近緣種 A. agallocha 產於"南洋". 亦有另一近緣種 A. malaccensis 產於孟加拉, 不丹, 印度, 印尼, 老撾, 馬來西亞, 緬甸, 菲律賓, 新加坡及泰國.
3. 至於"市面上"的情況之前應該未有討論, 市場上作為燒香, 藥物, 香料等, 商家可以從各地進貨甚至混雜. 據查, Aquilaria 屬樹木當受傷並經黴菌感染後, 即分泌帶有濃香的樹脂作自體保護, 此現象亦見於在其他樹木. 所謂"結香"即粘著已經硬化的樹脂的木塊或乾燥的樹脂. 相信三種 Aquilaria 生產樹脂的能力應該相若.
4. 廣義的"沉香" (A. agallocha & A. malaccensis) 產量或仍可支持目前的商業需求. 但就 A. sinensis 來說, 產量明顯已經不可能作為商業用途. 由於 A. sinensis 相當肯定曾廣布於華南包括香港, 因此有充分理由在香港實施保護及培育.
5. 海漆 Excoecaria agallocha 應該係一種生於濕地的耐鹽性紅樹, 只因其一個俗名為"土沉香"而被混淆, 與 Aquilaria 所有種應無大關係.




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