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Flying fox in Battambang, Cambodia
飞行狐狸在柬埔寨的Battambang。 Credit: Gefoto Stock / Alamy Stock Photo.
PUBLIC HEALTH
2021年2月5日12:00

科学家们对新的蝙蝠研究持怀疑态度,将气候变化与Covid-19出现联系起来

Ayesha Tandon

Ayesha Tandon

0.2。0.5.21
Ayesha Tandon

Ayesha Tandon

0.5.02.2021 | 12:00pm
公共卫生 科学家们对新的蝙蝠研究持怀疑态度,将气候变化与Covid-19出现联系起来

A new study suggests that climate change is enabling the evolution of new coronaviruses by creating “hotspots” for multiple bat species.

The study, published in the journalScience of the Total Environment发现中国南方云南省以及缅甸和老挝的邻近地区已成为过去世纪蝙蝠物种“丰富”的全球热点。

Around 40 species of bat have moved into the region, the authors say, bringing roughly 100 additional types of coronaviruses with them. This is due to climate change-induced changes in vegetation, they argue, adding that the “bat-borne ancestors” of SARS-CoV-1 and SARS-CoV-2 – the latter being the virus that causes Covid-19 – are thought to have originated there.

然而,许多没有参与研究的科学家表示,他们涉及研究中使用的数据和它所吸引的结论。人们讲碳简介中,这项亚慱官网研究使“太多的假设......得出结论,气候变化可能增加了这种方式发生了大流行的可能性”。

Impact of climate change on bat hotspots

The past century has seen changes in bat species richness – the number of bat species in a given region – across the world. The new study points to shifting vegetation types as a key factor behind these changes.

The map below shows changes in bat species richness between the two periods 1901-1930 and 1990-2019 that – the study says – have been driven by climate change-induced vegetation changes. The orange and red shading indicates a greater increase in bat species richness.

Estimated increase in the local number of bat species due to shifts in their geographical ranges driven by climate change between the 1901-1930 and 1990-2019 periods
由于1901年至1930年和1990 - 2019年期间,由于气候变化导致的地理范围的班班物种估计增加。云南 - 缅甸 - 老挝热点放大了盒子。来源:Beyer等。(2021.)。

地图显示云南(南方南部)和缅甸和老挝的邻近地区已经看到蝙蝠物种多样性的最大增加。这些是盒子里突出的深红色的区域。该研究中,中非也有一个值得注意的增加,加上若干地区中美洲和南美洲。

罗伯特博士博士, from theUniversity of Cambridge Zoology departmentand thePotsdam Institute for Climate Impacts Research,是这项研究的主要作者。他讲碳简单意见气候亚慱官网变化的影响正在扩大该地区蝙蝠的栖息地:

“我们知道整体地区本质上是富有的蝙蝠物种,但是我们的数据表明,其中许多蝙蝠无法使用一个世纪前的一部分当地环境。气候变化使许多这些栖息地更适合蝙蝠,让他们将他们的范围扩展到新的领域。“

These vegetation changes are being driven by higher atmospheric CO2 levels, increased temperature, changed rainfall patterns and reduced cloud cover, the study notes.

Focusing specifically on Yunnan, the plot below shows how habitats have shifted over the 20th century. The left side shows the 1901-1930 distribution of vegetation over the province, and the right side shows the 1990-2019 distribution.

Change in biome in the Yunnan-Myanmar-Laos area. 1901-1930 average compared to 1990-2019 average
Change in biome in the Yunnan-Myanmar-Laos area. 1901-1930 average compared to 1990-2019 average. Source: Beyer et al. (2021.)。

The plot indicates that over the 20th century, there was a significant shift from tropical shrublands to tropical savannahs and deciduous woodland. This is significant, the authors note, because more bat species can survive in a tropical savannah than in tropical forests.

下图显示了热带森林是绝大多数蝙蝠种类的合适栖息地。

Percentage-of-bat-species-that-can-live-in-different-habitat-types
Percentage of bat species that can live in different habitat types. Source: Beyer et al. (2021.)。

然而,作者注意到,还有其他因素可能影响未包含在研究中的蝙蝠种群。这些包括从人类活动,狩猎,侵袭性物种和污染的土地利用变化。

Bat-borne diseases

More than 60% of emerging infectious diseases in humans are “zoonotic” – meaning that they originate in animals. Last year, Carbon Brief published an解释者that unpacks how climate change and biodiversity disturbance could raise the risk of diseases being transmitted from animals to humans.

蝙蝠携带人畜共患病毒传染的比例最高ses out of all mammals. The world’s bat population carries roughly 3,000 different types of coronavirus, and each individual species harbours an average of 2.7 different coronaviruses alone.

The paper notes thatMiddle East Respiratory Syndrome(MERS), SARS CoV-1 – which is typically known as “SARS” (Severe Acute Respiratory Syndrome) – and SARS CoV-2 – the virus that causes Covid19 – are all thought to have originated in bats.

水果蝙蝠悬挂在树上 - 白天 - 岛, - 马来西亚
Fruit bats hanging on trees during day, Tioman Island, Malaysia.. Credit: Peter Conner / Alamy Stock Photo.

The paper estimates that climate change-driven changes in vegetation drew an extra 40 species of bats into the hotspot highlighted in the map, leading to roughly 100 more coronaviruses in the area.

Beyers tells Carbon Brief that this allows more opportunities for the virus to be transmitted or evolve, and may have been how SARS-CoV-2 shifted species:

“We estimate that the number of bat species, and of bat-borne coronaviruses, in the likely origin of SARS-CoV-2 has substantially increased due to climate-driven changes in the natural vegetation. This process has likely created significant new opportunities for the virus to be transmitted or evolve.”

这件作品指出,SARS-COV-2病毒被认为是在云南的蝙蝠中起源于蝙蝠,然后携带这些病毒的野生植物和野生动物在广东和武汉野生动物市场,在那里病毒首先开始感染人。

Sceptical reaction

To model the change in bat richness density, the authors created a map of the world’s vegetation usinga global temperature datasetand a植被模型。They then used information about the vegetation requirements of the world’s bat species to work out the global distribution of each species.

然而,许多科学家对所用方法和得出的结论是持怀疑态度。

Dr Dann Mitchell– joint Met Office chair in climate hazards at the布里斯托大学, who was not involved in the study – tells Carbon Brief about issues with the climate data used:

“Using some of our best climate observations, the authors identify a strong climate-driven signal over Myanmar and Laos, but there will be large uncertainties associated with variables such as cloud cover in that region, especially 100 years ago in South Asia – there is a lot of missing data there.”

Prof Paul Valdes, a professor of physical geography at the布里斯托大学, notes that although the paper is “interesting”, there are still “many untested aspects of their conclusions – especially since we are still debating the origins of Covid”.

Furthermore, to model bat species distributions, the authors rely on data from the国际保护性联盟bat specialist group.Dr Matthew Struebig, from theUniversity of Kent, is a member of the group, and warns that this map distribution data is “grossly insufficient”. He adds:

“Many species are not fully assessed, and too many are so poorly known they are only documented as a few dots on a map. Very little is known about optimum or preferred vegetation types – especially in the region highlighted in this study.

The study estimates the bat fauna of southern China and neighbouring countries increased by a whopping 40+ species in around 120 years. To put that into perspective, that would mean the number of bat species in Myanmar doubled in little over a century. Simply looking back at old species accounts and ecological studies from the region shows this simply did not happen.”

He adds that he is “sceptical of the link” between climate change and bat distribution change, and that the study makes “too many assumptions for me to conclude that climate change could have increased the likelihood of the pandemic occurring in this way”.

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Prof Paul Valdes, a professor of physical geography at the布里斯托大学, notes that although the paper is “interesting”, there are still “many untested aspects of their conclusions – especially since we are still debating the origins of Covid”.

他得出结论,它“似乎为止得出结论,气候变化对SARS-COV-2的出现产生了很大影响”。

Dr David Redding, a research fellow at theZoological Society of London, agrees, noting that “while it is useful to think about these types of links it is important to underpin these investigations with rigorous science”. He tells Carbon Brief:

“We know very little about the geographical origins of SARS or SARS-CoV-2. Indeed, the paper that is referenced by the authors to link the putative SE-Asia ‘hotspot’ to the possible origin of these pathogens, merely mentions that Vietnam and Laos were not examined by Chinese scientists and, therefore, could not be discounted as possible source locations.”

He adds that there are many other “missing links” in the research, for example that “we know very little about how many viruses circulate between individuals in host species”.

Prof Hans-Otto Poertner– head of biosciences at the阿尔弗雷德韦格纳研究所– tells Carbon Brief that though the analysis is “very interesting”, there are still “questions that are not clear” to him. This includes where the increase in species richness comes from, and whether there has been a timeseries of species observations supporting the modelled findings, he says.

AndProf Kate Jones- 生态学和生物多样性的主席University College London– stresses that although climate change “has a role to play in changing species distributions to increase ecological hazard”, there are other factors that are also important to consider.

She notes that the risk of “spillover” of a virus from a particular species to humans is a “complex interplay of not only ecological hazard but human exposure and vulnerability”. She adds:

“它可能会拒绝通过农业扩张的人口,人类运动和降低自然环境增加,在理解SARS-COV-2的溢出过程中,在理解SARS-COV-2的溢出过程中具有更重要的作用。”

Beyer, R. et al. (2021) Shifts in global bat diversity suggest a possible role of climate change in the emergence of SARS-CoV-1 and SARS-CoV-2, Science of the Total Environment, doi:10.。10.16/j.scitotenv.2021.145413

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