盜獵威脅仍在 兩非洲象獨立物種雙雙落入瀕危等級 | 環境資訊中心

盜獵威脅仍在 兩非洲象獨立物種雙雙落入瀕危等級

2021年03月30日
環境資訊中心外電;姜唯 翻譯;林大利 審校;稿源:ENS

過去50年間,象牙盜獵和棲地喪失帶給非洲象沉重的生存壓力。世界自然保育聯盟受脅物種紅皮書,現把非洲森林象列為極度瀕危級(Critically Endangered, CR),非洲莽原象列為瀕危級(Endangered, EN)。

非洲莽原象是陸地上最大的動物,被世界自然保育聯盟瀕危物種紅皮書列為瀕危級。照片來源:Ray in Manila(CC BY 2.0)

在此次更新前,非洲象被視為單一物種,受脅等級屬於易危級(Vulnerable, VU)。由於新的遺傳證據出現,世界自然保育聯盟(International Union for Conservation of Nature, IUCN)受脅物種紅皮書首次對這兩個物種分別進行評估。

2016年IUCN非洲象狀況報告對這兩種物種相加總數的最新可靠估計,大約是41萬5000頭。IUCN受脅物種紅皮書目前涵蓋13萬4425種物種,其中3萬7480種為受脅物種。

出現兩個獨立的非洲象物種

專家們根據最新大象族群遺傳學研究後,決定將非洲森林象(African Forest Elephant,學名:Loxodonta cyclotis)和非洲莽原象(African Savanna Elephant,學名:Loxodonta africana)視為兩個單獨的物種。還有第三種物種亞洲象,但此次評估未包含在內。

森林象生活在中非的熱帶森林和西非的許多棲地。牠們的生存範圍很少與非洲莽原象重疊。非洲莽原象喜歡開闊地區,生活在撒哈拉以南非洲的各種棲地中,包括草原和沙漠。

長期以來,人們一直認為非洲森林象是非洲象的一個亞種,現在許多科學家認為非洲莽原象和非洲森林象其實是兩個物種。非洲森林象體型比非洲莽原象小,象牙筆直且指向下方,與非洲莽原象的彎曲狀象牙不同。

非洲森林象的自然分布受影響較大,今日只剩過去活動範圍的1/4,加蓬和剛果共和國的剩餘數量最多。

根據肯亞非營利組織非洲野生動物基金會的說法,非洲森林象的繁殖速度是這三種大象中最慢的,性成熟年齡要到23歲,平均妊娠期約要兩年。在這種情況下,盜獵、獸肉貿易、伐木作業和自然資源開採而造成的個體數目減少,都更加具有破壞力。就算今天立刻停止盜獵,科學家說,要扭轉過去10年間62%的個體數量下降,還需要81年的時間。

非洲森林象體型比非洲莽原象小,象牙筆直且指向下方,目前在加蓬和剛果共和國的族群數量最多。照片來源:GRID-Arendal(CC BY-NC-SA 2.0)

盜獵、土地利用頻仍 非洲象族群處境堪憂

IUCN物種存續委員會主席羅德里格(Jon Paul Rodríguez)博士說,這樣的評估結果,有助將保育重點放在瀕危非洲森林象和非洲莽原象上。

IUCN物種存續委員會非洲象專家小組成員哥布許(Kathleen Gobush)博士說:「評估團隊成員有六位,使用最早可追溯至1960年代的資料,並採用完全以資料為基礎的建模方法,來整合許多科學團隊數十年來的研究工作。」

「評估結果量化了非洲象的族群衰退程度。由於象牙需求持續,加上人類帶給非洲原野地的壓力不斷上升,非洲象的處境很令人擔憂,運用創意保育和明智地管理這些動物及其棲地,急迫性比任何時候都要高。」

《保護野生動物遷徙物種公約(Conservation of Migratory Species of Wild Animals)》執行秘書弗蘭克爾(Amy Fraenkel)說,「非洲森林象和非洲莽原象,現已在公約附錄二列為兩個不同物種。」

由於盜獵增加,這兩種物種自2008年至今一直在減少。2011年盜獵活動達到巔峰後略見改善,但仍是大象的主要威脅。大象的棲地不斷轉化為農業和其他土地利用方式是另一個威脅。

最新評估顯示,整個非洲大陸的非洲象數量普遍下降,在過去31年間,非洲森林象數量下降了86%以上,非洲莽原象數量在過去50年間至少下降了60%。

保護區工作替非洲象帶來生機 反盜獵、土地利用規劃是關鍵

非洲象評估小組成員、IUCN物種存續委員會非洲象專家小組成員之一貝爾福(Dave Balfour)博士說:「雖然評估結果將非洲莽原象列為瀕危,但必須注意,在某些地點有些族群正在蓬勃發展。因此在將這些結果轉化為政策時,需要相當謹慎,並輔以地方知識。」

儘管這兩種非洲象整體呈現下降趨勢,但最新評估結果也顯示了成功的保育工作帶來的正面影響。 IUCN說,地面反盜獵措施和促進人類與野生動物共存的立法和土地利用規劃,是保護大象的關鍵,讓部分非洲森林象族群在加蓬和剛果共和國管理良好的保護區內穩定下來。

部分非洲莽原象族群的個體數量已保持穩定或成長了數十年,尤其是在卡萬戈-贊比西邊疆保護區(Kavango-Zambezi Transfrontier Conservation Area),這裡有非洲大陸上最大的草原象亞族群。

African Elephants Classed as Two Species, Both Endangered
GLAND, Switzerland, March 26, 2021 (ENS)

Poaching for ivory and loss of habitat over the past five decades have taken a grim toll on African elephants. The African forest elephant, Loxodonta cyclotis, is now listed as Critically Endangered and the African savanna elephant, Loxodonta africana, is listed as Endangered on the authoritative Red List of Threatened Species compiled by the International Union for the Conservation of Nature, IUCN.

Before today’s update, African elephants were treated as a single species, listed as Vulnerable to extinction. This is the first time the two species have been assessed separately for the IUCN Red List, after the emergence of new genetic evidence.

The 2016 IUCN African Elephant Status Report provides the most recent reliable estimate of the continental population of the two species combined, at around 415,000 elephants.

The IUCN Red List now covers 134,425 species of which 37,480 are threatened with extinction.

Two Separate African Elephant Species Emerge

The decision to treat African forest and savanna elephants as two separate species is the result of the consensus that has emerged among experts following new research into the genetics of elephant populations. There is also a third species, the Asian elephant, which is not covered in this assessment.

Forest elephants occur in the tropical forests of Central Africa and in a range of habitats in West Africa. They rarely overlap with the range of the savanna elephant, which prefers open country and is found in a variety of habitats in Sub-Saharan Africa including grasslands and deserts.

Long considered to be a subspecies of the African elephant, the African forest elephant is now believed by many scientists to be a species separate from the African savanna or bush elephant. They are smaller than the better-known savanna elephant, have tusks that are straight and point downward, unlike the savanna elephants’ curved tusks.

The forest elephant, which has a more restricted natural distribution, is thought to occupy only a quarter of its historic range today, with the largest remaining populations found in Gabon and the Republic of the Congo.

Forest elephants have the slowest reproductive rate of the three elephant species, according to the Kenya-based nonprofit African Wildlife Foundation. “The sexually mature age of these elephants is not until 23 and then the average gestation period is about two years. In this case, any population decline caused by poaching, bushmeat trade, logging operations, and natural resource extraction is more devastating. If poaching was stopped today, then scientists say it would take 81 years to reverse the 62 percent decline experienced in the last decade.”

Dr. Jon Paul Rodríguez, who chairs the IUCN Species Survival Commission, said, “These two Red List assessments reflect the outcome of the IUCN SSC African Elephant Specialist Group taking a bold, collaborative, evidence-based decision to assess the African elephant as two separate species for the first time and understanding the implications and consequences of this shift.”

“The outcome is robust assessments that provide users with the options to focus conservation efforts appropriately for the Critically Endangered forest elephant and the Endangered savanna elephant,” he said.

“For these assessments, a team of six assessors used data from as far back as the 1960s and a fully data-driven modeling approach to consolidate the decades-long efforts of many survey teams for the first time,” said Dr. Kathleen Gobush, lead assessor of the African elephants and member of the IUCN Species Survival Commission African Elephant Specialist Group.

“The results quantify the dramatic extent of the decline of these ecologically important animals. With persistent demand for ivory and escalating human pressures on Africa’s wildlands, concern for Africa’s elephants is high, and the need to creatively conserve and wisely manage these animals and their habitats is more acute than ever,” Dr. Gobush said.

“The Forest Elephant and the Savannah Elephant are already listed as two separate species on Appendix II of the Convention on Migratory Species,” said Amy Fraenkel, executive secretary of the Convention on the Conservation of Migratory Species of Wild Animals. “We welcome IUCN’s recognition of two distinct African elephant species and hope that it will lead to greater conservation actions for both species. In particular, the Forest Elephant has suffered drastic declines over the past few decades.”

The latest assessments reveal a broad decline in African elephant numbers across the continent. The number of African forest elephants fell by more than 86 percent over a period of 31 years, while the population of African savanna elephants decreased by at least 60 percent over the last 50 years, according to the assessments.

Both species have declined since 2008 due to an increase in poaching, which peaked in 2011 but continues to threaten elephant populations. The ongoing conversion of their habitats to agricultural and other land uses is another threat.

Dr. Dave Balfour, an assessor of the African elephants and member of the IUCN Species Survival Commission African Elephant Specialist Group, said, “While the results of the assessment place the continental population of savanna elephants in the Endangered category, it is important to keep in mind that at a site level, some subpopulations are thriving. For this reason, considerable caution and local knowledge are required when translating these results into policy.”

These latest assessments do show the impact of successful conservation efforts despite the overall declining trend of both African elephant species. Anti-poaching measures on the ground, together with more supportive legislation and land use planning which seeks to foster human-wildlife coexistence, have been key to successful elephant conservation, the IUCN says.

As a result, some forest elephants have stabilized in well-managed conservation areas in Gabon and the Republic of the Congo.

Savanna elephant numbers have also been stable or growing for decades especially in the Kavango-Zambezi Transfrontier Conservation Area, which harbors the largest subpopulation of this species on the continent.

※ 全文及圖片詳見:ENS

作者

姜唯

如果有一件事是重要的,如果能為孩子實現一個願望,那就是人類與大自然和諧共存。

林大利

於特有生物研究保育中心服務,小鳥和棲地是主要的研究對象。是龜毛的讀者,認為龜毛是探索世界的美德。