New study finds seabird response to abrupt climate change 5,000 years ago

November 05th 2020

New study finds seabird response to abrupt climate change 5,000 years ago

研究發現海⿃五千年前因應氣候變化⽽遷移 改變了亞南極島嶼的⽣態系統

 

The Falkland Islands are a South Atlantic refuge for some of the world’s most important seabird species, including five species of penguins, Great Shearwaters, and White-chinned Petrels. In recent years, their breeding grounds in the coastal tussac (Poa flabellata) grasslands have come under increasing pressure from sheep grazing and erosion. And unlike other regions of the globe, there has been no long-term monitoring of the responses of these burrowing and ground nesting seabirds to climate change.

福克蘭群島是全球⼀些最重要的海⿃族羣,包括五種企鵝、⼤海鷗和⽩額鸌在南⼤西洋的棲息庇護 之所。近年因為牧⽺作業和⼤⾃然侵蝕,⼀些海岸草地牠們的繁殖地正⾯臨⽇益嚴重的威脅。這些 海⿃在地上挖洞穴或在低地築巢棲息,受著氣候變化帶來的影響,然⽽不似在地球的其他角落,這 處地域仍然未有⼀套長期的監察系統,藉以了解在這裏棲息的海⿃族羣對氣候變化的反應。

A 14,000-year paleoecological reconstruction of the sub-Antarctic islands done by an international research team led by The University of Maine (UMaine) including Dr Moriaki YASUHARA from the School of Biological Sciences and The Swire Institute of Marine Science, The University of Hong Kong (HKU), has found that seabird establishment occurred during a period of regional cooling 5,000 years ago. Their populations, in turn, shifted the Falkland Island ecosystem through the deposit of high concentrations of guano that helped nourish tussac, produce peat and increase the incidence of fire. The findings were recently published in the journal Science Advances.

由⾹港⼤學(港⼤)⽣物科學學院及太古海洋科學研究所副教授安原盛明博⼠和美國緬因⼤學共同 領導的國際研究,重構了亞南極群島長達⼀萬四千年的古⽣態環境,發現在五千年前,該地域經歷 ⼀段寒化時期期間,海⿃族群便開始在那裏棲息。海⿃聚居為群島的⽣態系統帶來轉變,⼤量的⿃ 糞滋養了沿岸草地的泥⼟、形成泥煤,令⽕災更頻繁。研究團隊指出,隨著南⼤洋在今後幾⼗年間 逐漸變暖,福島的海⿃族群可能會經歷突變甚至崩潰,這在數⼗年間便有機會發⽣。研究結果剛於 學術期刊《科學前沿》(Science Advances)發表。

Nutrient inputs from seabirds 海⿃為福島泥⼟帶來養分

“This terrestrial-marine link is critical to the islands’ grasslands conservation efforts going forward,” says Dulcinea GROFF, who led the research as a PhD student in UMaine. “The connection of nutrients originating in the marine ecosystem that are transferred to the terrestrial ecosystem enrich the islands’ nutrient-poor soil, thereby making the Falkland Islands sensitive to changes in climate and land use. “Our work emphasizes just how important the nutrients in seabird poop are for the ongoing efforts to restore and conserve their grassland habitats. It also raises the question about where seabirds will go as the climate continues to warm,” said Groff, who conducted the research in the Falkland Islands during expeditions in 2014 and 2016 led by Jacquelyn GILL, an Associate Professor of paleoecology and plant ecology in the UMaine Climate Change Institute.

The UMaine expedition team collected a 476-centimeter peat column from Surf Bay, East Falkland. The 14,000-year record revealed in the undecomposed tussac leaves of the peat column captures the development of a terrestrial-marine linkage that supports some of the most important breeding colonies of seabirds in the Southern Ocean today.

The absence of seabirds at the East Falklands site prior to 5,000 years ago suggests that seabirds may be sensitive to warmer mediated sea surface temperatures, which can impact their food supply, according to the research team. With a warming South Atlantic today, the question is whether the Falkland Islands, about 300 miles east of South America, will continue to be a seabird breeding “hot spot”. The research team suggests that as the Southern Ocean continues to warm in the coming decades, the Falkland Islands seabird communities may undergo abrupt turnover or collapse, which could happen on the order of decades

領導今次研究的緬因⼤學博⼠⽣ Dulcinea GROFF 說:「海⿃是海洋與陸地的橋樑,這個重要的連 繫,對群島上草地保育⼯作的發展至為重要。」GROFF 解釋:「養分經海⿃由海洋的⽣態系統轉到 陸地的⽣態系統,滋養島上原來貧瘠的⼟地,這讓福島很容易因應氣候變化,⼟壤和⽤途都會改 變。」 GROFF 於 2014 和 2016 年間曾跟隨導師緬因⼤學古⽣物和植物⽣態研究學者 Jacquelyn GILL 博⼠到 福克蘭群島進⾏實地勘察研究。「我們的研究顯⽰,海⿃糞所提供的養分,對重建和保育海⿃的棲 息草地非常重要。這亦引申出⼀個問題,當氣候持續暖化,海⿃會在那裏落脚棲息。」GROFF 説。 緬因⼤學的考察隊從東福克蘭群島 Surf Bay 採集了⼀條 476 厘⽶長的泥煤岩芯,當中記錄了該地域 ⼀萬四千年來⽣態環境的轉變,泥煤中未被分解的草葉揭⽰了這個重要關連,即養分透過海⿃從海 洋轉移到陸地,⽀持著今天⼀些在南冰洋的最重要海⿃的繁殖區和棲息地。研究團隊認爲,從五千 Pokfulam Road Tel: (852) 3917 2683 Fax: (852) 2858 4620 E-mail: science@hku.hk Website: https://www.scifac.hku.hk/ 年前東福克蘭群島仍未⾒海⿃的蹤影,可推論海⿃可能對較溫暖的海⾯溫度比較敏感,因爲海⽔溫 度會影響牠們的覓食機會。問題是,今天南⼤西洋逐漸變暖,在南美東⾯ 300 ⾥外的福島能否維持 作爲海⿃繁殖地的「熱點」。研究團隊認爲,隨著南⼤洋在今後幾⼗年間逐漸變暖,福島的海⿃種 群可能會經歷突變甚至崩潰,這在數⼗年間便有機會發⽣。

The 14,000-year record from East Falkland revealed that for 9,000 years before the arrival of seabirds, the region was dominated by low levels of grasses, a heathland of ferns and dwarf Ericaceous shrubs. About 5,000 years ago, the researchers says, an “abrupt transition” appears to occur. Concentrations in bio-elements such as phosphorus and zinc increase. Grass pollen accumulation rates skyrocket, indicating the establishment of tussac grasslands within 200 years of the establishment of seabird colonies on the island. Also found in the core: increased accumulation rates of peat and charcoal. “This timing is consistent with that of the Southern Ocean cooling that known paleoclimatic records consistently indicate.”, said Yasuhara, a paleoecologist and paleoclimatologist in HKU, who is familiar with polar paleoclimatology and paleoceanography.

從記錄了古⽣態環境轉變的泥煤岩芯,可⾒在海⿃抵埗前的九千年間,該地域主要由低等植物佔 據,是⼀⽚長滿蕨類和矮灌⽊的荒原。研究⼈員指出,⼤約五千年前,該處似乎經歷了⼀次「驟然 過渡」。⼀些⽣物元素像磷和鋅的濃度增加,草類植物花粉積聚爆發式上升,顯⽰在島上海⿃族群 形成的兩百年間草地正茂盛⽣長︔岩芯也揭⽰這段時期泥煤與⽊炭的積累速度在增加。港⼤安原盛 明博⼠指出:「這時期所發⽣的,與古氣候學所記錄南⼤洋變冷的時間⼀致。」安原盛明博⼠是古 ⽣態和古氣候學者,尤其熟悉極地古氣候與古海洋學。

It is clear that the addition of seabird populations bringing nutrients from the marine environment to the island drove changes in the terrestrial plant community structure, composition and function, as well as increased fire activity and nutrient cycling. What remains unclear is what drove the abrupt ecosystem shift, including the impacts of climate change and extinction, and the geographical distribution of living things through space and time.

研究結果表明,海⿃數量增加把養分從海洋帶到陸地,促成陸地植物群落在結構、功能與組成上的 轉變,山⽕和營養循環也有所增加。⽬前仍然不清楚的,是甚麼導致⽣態系統的驟變,當中包括氣 候變化和⽣物滅絕帶來的影響,以及⽣物在不同時空的地理分佈。

“Our study is also a powerful reminder of why we need to understand how different ecosystems are connected as the world warms,” says Gill. “Such understanding is especially important in polar regions and ecosystems that are known to be sensitive to climate change,” continues Yasuhara. Gill concluded, “We know that many seabirds in the South Atlantic rely on these unique coastal grasslands, but it turns out that the grasses also depend on the nutrients seabirds provide. Because they rely on ecosystems in the ocean and on land for their survival, seabirds are really excellent sentinels of global change. We just don’t have good long-term monitoring data for most of these species, so we don’t know enough about how sensitive they are to climate change. The fossil record can help us fill in the gaps.”

Gill 博⼠說:「⼈們有需要了解在地球暖化的情況下,不同⽣態系統是如何互動和相關連,我們的 研究對此有很⼤的提醒作⽤。」安原盛明博⼠補充說:「這些理解對於極地地區以及對氣候變化相 對敏感的⽣態系統尤其重要。」Gill 博⼠總結道:「我們知道南⼤西洋的許多海⿃依賴這些獨特的 沿海草地⽽⽣,這些草地也靠海⿃所提供的養分得以維持。⽽正因為海⿃全依賴海洋與陸地的⽣態 系統以⽣存,牠們是全球變化的重要警⽰。可惜我們沒有相關物種的長期監測數據,因⽽不⾜以了 解牠們對氣候變化的敏感度。這些化⽯記錄正好幫助我們填補這個缺⼜。」

Link of the journal paper: https://advances.sciencemag.org/content/6/43/eabb2788

Science Advances 的論⽂連結https://advances.sciencemag.org/content/6/43/eabb2788

For media enquiries, please contact Ms Casey To, External Relations Officer of HKU Faculty of Science (tel: 3917 4948; email: caseyto@hku.hk) , Ms Cindy Chan, Assistant Director of Communications (tel: 3917 5286; email: cindycst@hku.hk).

傳媒如有查詢,請聯絡港⼤理學院外務主任杜之樺(電話: 3917 4948; 電郵: caseyto@hku.hk)/助理傳 訊總監陳詩迪(電話: 3917 5286; 電郵: cindycst@hku.hk)。

Images download and captions: https://www.scifac.hku.hk/press

相⽚下載https://www.scifac.hku.hk/press

全部圖⽚由 Dulcinea GROFF 提供。

Image 1. A rookery of black-browed albatross (Thalassarche melanophris) nest at a windy, exposed tussac grassland on West Point Island, Falkland Islands. Photo courtesy: Dulcinea GROFF

圖⼀:⿊眉信天翁在多風、暴露的草地棲 息地上築巢。

Image 2. A rookery of Southern rockhopper penguins (Eudyptes chrysocome chrysocome) nest between a rocky slope and a tussac grassland and bring in nutrients from the ocean directly to the grasses at the Kidney Island National Nature Reserve, Falkland Islands. Photo courtesy: Dulcinea GROFF

圖⼆:南跳岩企鵝在⽯頭海岸與草地之間築巢。牠 們直接把營養從海洋帶到草地。圖⽚攝於福克蘭困 島國家⾃然保護區。

Image 3. On a summer day, a Magellanic penguin (Spheniscus magellanicus) rests on a pedestal outside of their burrow in the peat of the tussac grassland, East Falkland Island, Falkland Islands. Photo courtesy: Dulcinea GROFF

圖三:夏天的時候,⼀隻⿆哲倫企鵝站在 洞穴外⾯的草地上的泥煤塊上休息。

Image 4. In the Falkland Islands, tussac grasslands that form deep peat deposits can be found eroding along some coastlines. Photo courtesy: Dulcinea GROFF

圖四:福克蘭群島的海岸線,可看到由草原形成的 厚實沉積物有被侵蝕的跡象。

Image 5. At dusk thousands of seabirds called sooty shearwaters (Ardenna grisea) return to their deep nesting burrows dug into the peat of the tussac grassland at the Kidney Island National Nature Reserve, Falkland Islands. Photo courtest: Dulcinea Groff.

圖五:⿈昏時,幾千隻灰鸌回到位於草地泥煤上的深巢洞穴裏。圖⽚攝於福克蘭島 Kindey 島國 家⾃然保護區。

 

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