Geometry and scale in species-area relationships

Arising from F. He & S. P. Hubbell 473, 368-371 (2011). He and Hubbell developed a sampling theory for the species-area relationship (SAR) and the endemics-area relationship (EAR). They argued that the number of extinctions after habitat loss is described by the EAR and that extinction rates in previous studies are overestimates because the EAR is always lower than the SAR. Here we show that their conclusion is not general and depends on the geometry of habitat destruction and the scale of the SAR. We also question their critique of the Millennium Ecosystem Assessment estimates, as those estimates are not dependent on the SAR only, although important uncertainties remain due to other methodological issues.     

Species-specific responses of Late Quaternary megafauna to climate and humans

Despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during the Late Quaternary period remain contentious. Here we use ancient DNA, species distribution models and the human fossil record to elucidate how climate and humans shaped the demographic history of woolly rhinoceros, woolly mammoth, wild horse, reindeer, bison and musk ox. We show that climate has been a major driver of population change over the past 50,000 years. However, each species responds differently to the effects of climatic shifts, habitat redistribution and human encroachment. Although climate change alone can explain the extinction of some species, such as Eurasian musk ox and woolly rhinoceros, a combination of climatic and anthropogenic effects appears to be responsible for the extinction of others, including Eurasian steppe bison and wild horse. We find no genetic signature or any distinctive range dynamics distinguishing extinct from surviving species, emphasizing the challenges associated with predicting future responses of extant mammals to climate and human-mediated habitat change.     

Extinction risk from climate change

Climate change over the past approximately 30 years has produced numerous shifts in the distributions and abundances of species and has been implicated in one species-level extinction. Using projections of species' distributions for future climate scenarios, we assess extinction risks for sample regions that cover some 20% of the Earth's terrestrial surface. Exploring three approaches in which the estimated probability of extinction shows a power-law relationship with geographical range size, we predict, on the basis of mid-range climate-warming scenarios for 2050, that 15-37% of species in our sample of regions and taxa will be 'committed to extinction'. When the average of the three methods and two dispersal scenarios is taken, minimal climate-warming scenarios produce lower projections of species committed to extinction ( approximately 18%) than mid-range ( approximately 24%) and maximum-change ( approximately 35%) scenarios. These estimates show the importance of rapid implementation of technologies to decrease greenhouse gas emissions and strategies for carbon sequestration.     

Species-area relationships always overestimate extinction rates from habitat loss

Extinction from habitat loss is the signature conservation problem of the twenty-first century. Despite its importance, estimating extinction rates is still highly uncertain because no proven direct methods or reliable data exist for verifying extinctions. The most widely used indirect method is to estimate extinction rates by reversing the species-area accumulation curve, extrapolating backwards to smaller areas to calculate expected species loss. Estimates of extinction rates based on this method are almost always much higher than those actually observed. This discrepancy gave rise to the concept of an 'extinction debt', referring to species 'committed to extinction' owing to habitat loss and reduced population size but not yet extinct during a non-equilibrium period. Here we show that the extinction debt as currently defined is largely a sampling artefact due to an unrecognized difference between the underlying sampling problems when constructing a species-area relationship (SAR) and when extrapolating species extinction from habitat loss. The key mathematical result is that the area required to remove the last individual of a species (extinction) is larger, almost always much larger, than the sample area needed to encounter the first individual of a species, irrespective of species distribution and spatial scale. We illustrate these results with data from a global network of large, mapped forest plots and ranges of passerine bird species in the continental USA; and we show that overestimation can be greater than 160%. Although we conclude that extinctions caused by habitat loss require greater loss of habitat than previously thought, our results must not lead to complacency about extinction due to habitat loss, which is a real and growing threat.     

Climate change threats to protected plants of China: an evaluation based on species distribution modeling

Climate change poses major new challenges to biodiversity conservation. Distribution ranges of species have been proven to be affected by climate anomalies. Detecting the extent of protected species response to climate change can help formulate flexible conservation strategies to overcome the changing climate. Using species distribution modeling and high resolution climate data, we simulated current distribution patterns of 233 protected plants in China. Those patterns were then projected into future suitable habitats for each species under nine climate change scenarios, with no migration or full migration hypotheses. Under the most extreme climate change scenario （CGCM-B2a）, we evaluated species extinction risks. Sixteen percent of protected plants are expected to lose more than 30 % of their current ranges. By calculating areal shifts, hotspots for emigrants, immigrants, and persistent species were identified under climate change. Flexible conservation strategies were addressed for those regions. Those strategies strongly depend on the migration types of species and sensitivity of the hotspots to changing climate. In hotspots for emigrants, the main conservation strategy is ex situ protection; protected species from these regions should be stored in seed banks or botanical gardens. For hotspots of immigrants, enough space should be maintained for new species, and some measures are necessary to assist dispersal. For hotspots of persistent species, more natural reserves are needed. We highlight related fields that can help conserve protected species in the future, such as conserving the soil seed bank and understanding of the effects of migration ability and interactions between protected species.     

Rapid responses of British butterflies to opposing forces of climate and habitat change.

Habitat degradation and climate change are thought to be altering the distributions and abundances of animals and plants throughout the world, but their combined impacts have not been assessed for any species assemblage. Here we evaluated changes in the distribution sizes and abundances of 46 species of butterflies that approach their northern climatic range margins in Britain-where changes in climate and habitat are opposing forces. These insects might be expected to have responded positively to climate warming over the past 30 years, yet three-quarters of them declined: negative responses to habitat loss have outweighed positive responses to climate warming. Half of the species that were mobile and habitat generalists increased their distribution sites over this period (consistent with a climate explanation), whereas the other generalists and 89% of the habitat specialists declined in distribution size (consistent with habitat limitation). Changes in population abundances closely matched changes in distributions. The dual forces of habitat modification and climate change are likely to cause specialists to decline, leaving biological communities with reduced numbers of species and dominated by mobile and widespread habitat generalists.     

Universal species-area and endemics-area relationships at continental scales

Despite the broad conceptual and applied relevance of how the number of species or endemics changes with area (the species-area and endemics-area relationships (SAR and EAR)), our understanding of universality and pervasiveness of these patterns across taxa and regions has remained limited. The SAR has traditionally been approximated by a power law, but recent theories predict a triphasic SAR in logarithmic space, characterized by steeper increases in species richness at both small and large spatial scales. Here we uncover such universally upward accelerating SARs for amphibians, birds and mammals across the world’s major landmasses. Although apparently taxon-specific and continent-specific, all curves collapse into one universal function after the area is rescaled by using the mean range sizes of taxa within continents. In addition, all EARs approximately follow a power law with a slope close to 1, indicating that for most spatial scales there is roughly proportional species extinction with area loss. These patterns can be predicted by a simulation model based on the random placement of contiguous ranges within a domain. The universality of SARs and EARs after rescaling implies that both total and endemic species richness within an area, and also their rate of change with area, can be estimated by using only the knowledge of mean geographic range size in the region and mean species richness at one spatial scale.     

Parallel extinction risk and global distribution of languages and species

There are global threats to biodiversity with current extinction rates well above background levels. Although less well publicized, numerous human languages have also become extinct, and others are threatened with extinction. However, estimates of the number of threatened languages vary considerably owing to the wide range of criteria used. For example, languages have been classified as threatened if the number of speakers is less than 100, 500, 1,000, 10,000, 20,000 or 100,000 (ref. 3). Here I show, by applying internationally agreed criteria for classifying species extinction risk, that languages are more threatened than birds or mammals. Rare languages are more likely to show evidence of decline than commoner ones. Areas with high language diversity also have high bird and mammal diversity and all three show similar relationships to area, latitude, area of forest and, for languages and birds, maximum altitude. The time of human settlement has little effect on current language diversity. Although similar factors explain the diversity of languages and biodiversity, the factors explaining extinction risk for birds and mammals (high altitude, high human densities and insularity) do not explain the numbers of endangered languages.     

Impact of regional climate change on human health

The World Health Organisation estimates that the warming and precipitation trends due to anthropogenic climate change of the past 30 years already claim over 150,000 lives annually. Many prevalent human diseases are linked to climate fluctuations, from cardiovascular mortality and respiratory illnesses due to heatwaves, to altered transmission of infectious diseases and malnutrition from crop failures. Uncertainty remains in attributing the expansion or resurgence of diseases to climate change, owing to lack of long-term, high-quality data sets as well as the large influence of socio-economic factors and changes in immunity and drug resistance. Here we review the growing evidence that climate-health relationships pose increasing health risks under future projections of climate change and that the warming trend over recent decades has already contributed to increased morbidity and mortality in many regions of the world. Potentially vulnerable regions include the temperate latitudes, which are projected to warm disproportionately, the regions around the Pacific and Indian oceans that are currently subjected to large rainfall variability due to the El Ni?o/Southern Oscillation sub-Saharan Africa and sprawling cities where the urban heat island effect could intensify extreme climatic events.     

Changes in plant community composition lag behind climate warming in lowland forests

Climate change is driving latitudinal and altitudinal shifts in species distribution worldwide, leading to novel species assemblages. Lags between these biotic responses and contemporary climate changes have been reported for plants and animals. Theoretically, the magnitude of these lags should be greatest in lowland areas, where the velocity of climate change is expected to be much greater than that in highland areas. We compared temperature trends to temperatures reconstructed from plant assemblages (observed in 76,634 surveys) over a 44-year period in France (1965-2008). Here we report that forest plant communities had responded to 0.54 °C of the effective increase of 1.07 °C in highland areas (500-2,600 m above sea level), while they had responded to only 0.02 °C of the 1.11 °C warming trend in lowland areas. There was a larger temperature lag (by 3.1 times) between the climate and plant community composition in lowland forests than in highland forests. The explanation of such disparity lies in the following properties of lowland, as compared to highland, forests: the higher proportion of species with greater ability for local persistence as the climate warms, the reduced opportunity for short-distance escapes, and the greater habitat fragmentation. Although mountains are currently considered to be among the ecosystems most threatened by climate change (owing to mountaintop extinction), the current inertia of plant communities in lowland forests should also be noted, as it could lead to lowland biotic attrition.     

Neutral theory and relative species abundance in ecology

The theory of island biogeography asserts that an island or a local community approaches an equilibrium species richness as a result of the interplay between the immigration of species from the much larger metacommunity source area and local extinction of species on the island (local community). Hubbell generalized this neutral theory to explore the expected steady-state distribution of relative species abundance (RSA) in the local community under restricted immigration. Here we present a theoretical framework for the unified neutral theory of biodiversity and an analytical solution for the distribution of the RSA both in the metacommunity (Fisher's log series) and in the local community, where there are fewer rare species. Rare species are more extinction-prone, and once they go locally extinct, they take longer to re-immigrate than do common species. Contrary to recent assertions, we show that the analytical solution provides a better fit, with fewer free parameters, to the RSA distribution of tree species on Barro Colorado Island, Panama, than the lognormal distribution.     

气候变化风险下中国建筑和土木工程设计参数分析

 通过气象、建筑和土木工程领域的学科交叉，梳理了目前中国建筑及土木工程设计标准中的部分设计用气象参数，并与几种相关的典型气候变化风险下的预估数据进行对比，表明为了更好地应对未来变化，上述部分参数需要进行相应调整。提出了对这些参数进行历史数据更新、增加未来气候变化风险维度的框架建议。构建了针对单个建设项目应对未来气候变化风险专项设计用气象参数预估的设想。     

Ecological and evolutionary processes at expanding range margins

Many animals are regarded as relatively sedentary and specialized in marginal parts of their geographical distributions. They are expected to be slow at colonizing new habitats. Despite this, the cool margins of many species' distributions have expanded rapidly in association with recent climate warming. We examined four insect species that have expanded their geographical ranges in Britain over the past 20 years. Here we report that two butterfly species have increased the variety of habitat types that they can colonize, and that two bush cricket species show increased fractions of longer-winged (dispersive) individuals in recently founded populations. Both ecological and evolutionary processes are probably responsible for these changes. Increased habitat breadth and dispersal tendencies have resulted in about 3- to 15-fold increases in expansion rates, allowing these insects to cross habitat disjunctions that would have represented major or complete barriers to dispersal before the expansions started. The emergence of dispersive phenotypes will increase the speed at which species invade new environments, and probably underlies the responses of many species to both past and future climate change.     

Uncertainty in predictions of the climate response to rising levels of greenhouse gases

The range of possibilities for future climate evolution needs to be taken into account when planning climate change mitigation and adaptation strategies. This requires ensembles of multi-decadal simulations to assess both chaotic climate variability and model response uncertainty. Statistical estimates of model response uncertainty, based on observations of recent climate change, admit climate sensitivities--defined as the equilibrium response of global mean temperature to doubling levels of atmospheric carbon dioxide--substantially greater than 5 K. But such strong responses are not used in ranges for future climate change because they have not been seen in general circulation models. Here we present results from the 'climateprediction.net' experiment, the first multi-thousand-member grand ensemble of simulations using a general circulation model and thereby explicitly resolving regional details. We find model versions as realistic as other state-of-the-art climate models but with climate sensitivities ranging from less than 2 K to more than 11 K. Models with such extreme sensitivities are critical for the study of the full range of possible responses of the climate system to rising greenhouse gas levels, and for assessing the risks associated with specific targets for stabilizing these levels.     

中国珍稀植物濒危原因及保护对策研究进展

珍稀濒危植物由于自身的原因或受到人类活动的影响,现存数量稀少或者只出现在脆弱的有限生境中,面临随时可能灭绝的威胁。中国是世界上植物多样性最丰富的国家之一,但在过去50年里,我国有数千种植物已经或濒临灭绝,植物保护工作的形势十分严峻。研究探讨珍稀濒危植物数量稀少的原因,并采取积极措施保护珍稀濒危植物种质资源,已成为中国生物多样性研究亟待解决的问题。本文基于文献资料对中国珍稀濒危植物的现状及原因进行分析,归纳出导致植物濒危的因素包括内因和外因两方面,其中内因主要是植物自身遗传多样性低、繁殖能力不足或幼苗活力弱,外因主要是指历史气候和生境的变迁、同域物种竞争以及人类活动的影响。     

Additive threats from pathogens, climate and land-use change for global amphibian diversity

Amphibian population declines far exceed those of other vertebrate groups, with 30% of all species listed as threatened by the International Union for Conservation of Nature. The causes of these declines are a matter of continued research, but probably include climate change, land-use change and spread of the pathogenic fungal disease chytridiomycosis. Here we assess the spatial distribution and interactions of these primary threats in relation to the global distribution of amphibian species. We show that the greatest proportions of species negatively affected by climate change are projected to be found in Africa, parts of northern South America and the Andes. Regions with the highest projected impact of land-use and climate change coincide, but there is little spatial overlap with regions highly threatened by the fungal disease. Overall, the areas harbouring the richest amphibian faunas are disproportionately more affected by one or multiple threat factors than areas with low richness. Amphibian declines are likely to accelerate in the twenty-first century, because multiple drivers of extinction could jeopardize their populations more than previous, mono-causal, assessments have suggested.     

未来气候变化情景下我国粮食供需平衡风险研究

“粮食供需平衡风险”定义为未来气候变化对我国粮食供需的影响程度。基于IPCC 排放情景特别报告(SRES)中B2情景气候条件下的我国粮食生产模拟结果, 构建该框架下我国粮食消费分析情景, 最终建立以自给粮食供应程度为核心的粮食供需平衡风险标准。借助GIS空间分析技术, 探讨县域尺度上近期、中期和远期的气候变化将会给我国粮食供需平衡带来怎样的风险局面。结果表明气候变化将会在一定程度上加剧我国的粮食供需平衡形势。3个时段内, 粮食供需风险局面严峻形势由高到低排序: 中期>远期>近期。具体地, 中期面临的供需风险的县市比例高达66.99%, 其中中风险和高风险区域范围最广, 两者所占比例高达29.5%; 近期风险形势相对较为缓和, 上述比例降低到25.54%, 其中高风险县市比例较低约为10.72%, 中风险约为14.82%; 在空间格局上, 黄淮海区、黄土高原区、西南区以及青藏区的东缘面临的风险形势相对较为严峻, 东北区、甘新区以及内蒙及长城沿线区则相对较为良好。     

Climate sensitivity constrained by CO2 concentrations over the past 420 million years

A firm understanding of the relationship between atmospheric carbon dioxide concentration and temperature is critical for interpreting past climate change and for predicting future climate change. A recent synthesis suggests that the increase in global-mean surface temperature in response to a doubling of the atmospheric carbon dioxide concentration, termed 'climate sensitivity', is between 1.5 and 6.2 degrees C (5-95 per cent likelihood range), but some evidence is inconsistent with this range. Moreover, most estimates of climate sensitivity are based on records of climate change over the past few decades to thousands of years, when carbon dioxide concentrations and global temperatures were similar to or lower than today, so such calculations tend to underestimate the magnitude of large climate-change events and may not be applicable to climate change under warmer conditions in the future. Here we estimate long-term equilibrium climate sensitivity by modelling carbon dioxide concentrations over the past 420 million years and comparing our calculations with a proxy record. Our estimates are broadly consistent with estimates based on short-term climate records, and indicate that a weak radiative forcing by carbon dioxide is highly unlikely on multi-million-year timescales. We conclude that a climate sensitivity greater than 1.5 degrees C has probably been a robust feature of the Earth's climate system over the past 420 million years, regardless of temporal scaling.     

A global synthesis reveals biodiversity loss as a major driver of ecosystem change

Evidence is mounting that extinctions are altering key processes important to the productivity and sustainability of Earth's ecosystems. Further species loss will accelerate change in ecosystem processes, but it is unclear how these effects compare to the direct effects of other forms of environmental change that are both driving diversity loss and altering ecosystem function. Here we use a suite of meta-analyses of published data to show that the effects of species loss on productivity and decomposition--two processes important in all ecosystems--are of comparable magnitude to the effects of many other global environmental changes. In experiments, intermediate levels of species loss (21-40%) reduced plant production by 5-10%, comparable to previously documented effects of ultraviolet radiation and climate warming. Higher levels of extinction (41-60%) had effects rivalling those of ozone, acidification, elevated CO(2) and nutrient pollution. At intermediate levels, species loss generally had equal or greater effects on decomposition than did elevated CO(2) and nitrogen addition. The identity of species lost also had a large effect on changes in productivity and decomposition, generating a wide range of plausible outcomes for extinction. Despite the need for more studies on interactive effects of diversity loss and environmental changes, our analyses clearly show that the ecosystem consequences of local species loss are as quantitatively significant as the direct effects of several global change stressors that have mobilized major international concern and remediation efforts.     

气候变化下西南地区12种常见针叶树种适宜分布区预测

【目的】随气候变化加剧,未来西南地区针叶林分布存在诸多不确定性,进行未来气候下西南地区常见针叶树种适宜分布区研究,为该地区森林生态安全评估提供参考。【方法】基于最大熵模型(MaxEnt)模拟未来气候情景下西南地区常见的12种针叶树的气候适宜分布区。【结果】MaxEnt模型能够很好地模拟西南地区12个树种的潜在分布,AUC值均达0.9以上; 2070年MPI-ESM-LR模式RCP4.5情景下西南地区12种常见针叶树种气候适宜区面积分布变化显著,包括冷杉、三尖杉、杉木、干香柏、柏木、水杉、云南松、红豆杉和福建柏在内的9个树种气候适宜区与气候最适区面积增加11.1%~412.8%;银杉和油麦吊云杉的气候适宜区面积分别增加6.0%和32.8%,但气候最适区面积减少了0.8%和3.5%;云南油杉未来气候适宜区和气候最适区的面积则减少24.0%和29.1%。【结论】西南地区针叶林中广布树种的气候适宜区面积会得益于气候变化而扩大,但云南油杉和油麦吊云杉等一些西南特有乡土树种的气候适宜区面积则会因为气候变化而缩小,因此对特有乡土树种的保护应给予重视。