Scenarios of changes in biodiversity for the year 2100 can now be developed based on scenarios of changes in atmospheric carbon dioxide, climate, vegetation, and land use and the known sensitivity of biodiversity to these changes. This study identified a ranking of the importance of drivers of change, a ranking of the biomes with respect to expected changes, and the major sources of uncertainties. For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration. For freshwater ecosystems, biotic exchange is much more important. Mediterranean climate and grassland ecosystems likely will experience the greatest proportional change in biodiversity because of the substantial influence of all drivers of biodiversity change. Northern temperate ecosystems are estimated to experience the least biodiversity change because major land-use change has already occurred. Plausible changes in biodiversity in other biomes depend on interactions among the causes of biodiversity change. These interactions represent one of the largest uncertainties in projections of future biodiversity change.
onto ecosystem functioning and human well-being. Much remains unknown about 28 this "Anthropocene defaunation"; these knowledge gaps hinder our capacity to 29 predict and limit defaunation impacts. Clearly, however, defaunation is both a 30 pervasive component of the planet's sixth mass extinction, and also a major driver of 31 global ecological change. 32 33In the past 500 years, humans have triggered a wave of extinction, threat, and local 34 population declines that may be comparable in both rate and magnitude to the five 35 previous mass extinctions of Earth's history (1). Similar to other mass extinction events, 36 the effects of this "sixth extinction wave" extend across taxonomic groups, but are also 37 selective, with some taxonomic groups and regions being particularly affected (2). Here, 38we review the patterns and consequences of contemporary anthropogenic impact on 39 terrestrial animals. We aim to portray the scope and nature of declines of both species and 40 abundance of individuals, and examine the consequences of these declines. So profound 41 is this problem, that we have applied the term defaunation to describe it. This recent pulse 42 of animal loss, hereafter referred to as the Anthropocene defaunation, is not only a 43 conspicuous consequence of human impacts on the planet, but also a primary driver of 44 global environmental change in its own right. In comparison, we highlight the profound 45 ecological impacts of the much more limited extinctions, predominantly of larger 46vertebrates, that occurred during the end of the last Ice Age. These extinctions altered 47 ecosystem processes and disturbance regimes at continental scales, triggering cascades of 48 extinction thought to still reverberate today (3, 4). 49The term defaunation, used to denote the loss of both species and populations of 50 wildlife (5), as well as local declines in abundance of individuals, needs to be considered 51 in the same sense as deforestation, a term that is now readily recognized and influential in 52 focusing scientific and general public attention on biodiversity issues (5). However, 53 whilst remote sensing technology provides rigorous quantitative information and 54 compelling images of the magnitude, rapidity and extent of patterns of deforestation, 55 defaunation remains a largely cryptic phenomenon. It can occur even in large protected 56 habitats (6) and, yet, some animal species are able to persist in highly modified habitats, 57 making it difficult to quantify without intensive surveys. 58Analyses of the impacts of global biodiversity loss typically base their 59 conclusions on data derived from species extinctions (1, 7, 8) and typically evaluations of 60 the effects of biodiversity loss draw heavily from small scale manipulations of plants and 61 small sedentary consumers (9). Both of these approaches likely underestimate the full 62 impacts of biodiversity loss. While species extinctions are of great evolutionary 63 significance, declines in the number of individuals in local populations and chan...
The population extinction pulse we describe here shows, from a quantitative viewpoint, that Earth's sixth mass extinction is more severe than perceived when looking exclusively at species extinctions. Therefore, humanity needs to address anthropogenic population extirpation and decimation immediately. That conclusion is based on analyses of the numbers and degrees of range contraction (indicative of population shrinkage and/or population extinctions according to the International Union for Conservation of Nature) using a sample of 27,600 vertebrate species, and on a more detailed analysis documenting the population extinctions between 1900 and 2015 in 177 mammal species. We find that the rate of population loss in terrestrial vertebrates is extremely high-even in "species of low concern." In our sample, comprising nearly half of known vertebrate species, 32% (8,851/27,600) are decreasing; that is, they have decreased in population size and range. In the 177 mammals for which we have detailed data, all have lost 30% or more of their geographic ranges and more than 40% of the species have experienced severe population declines (>80% range shrinkage). Our data indicate that beyond global species extinctions Earth is experiencing a huge episode of population declines and extirpations, which will have negative cascading consequences on ecosystem functioning and services vital to sustaining civilization. We describe this as a "biological annihilation" to highlight the current magnitude of Earth's ongoing sixth major extinction event.sixth mass extinction | population declines | population extinctions | conservation | ecosystem service
Biodiversity, a central component of Earth's life support systems, is directly relevant to human societies. We examine the dimensions and nature of the Earth's terrestrial biodiversity and review the scientific facts concerning the rate of loss of biodiversity and the drivers of this loss. The estimate for the total number of species of eukaryotic organisms possible lies in the 5-15 million range, with a best guess of ∼7 million. Species diversity is unevenly distributed; the highest concentrations are in tropical ecosystems. Endemisms are concentrated in a few hotspots, which are in turn seriously threatened by habitat destruction-the most prominent driver of biodiversity loss. For the past 300 years, recorded extinctions for a few groups of organisms reveal rates of extinction at least several hundred times the rate expected on the basis of the geological record.
Terrestrial mammals are experiencing a massive collapse in their population sizes and geographical ranges around the world, but many of the drivers, patterns and consequences of this decline remain poorly understood. Here we provide an analysis showing that bushmeat hunting for mostly food and medicinal products is driving a global crisis whereby 301 terrestrial mammal species are threatened with extinction. Nearly all of these threatened species occur in developing countries where major coexisting threats include deforestation, agricultural expansion, human encroachment and competition with livestock. The unrelenting decline of mammals suggests many vital ecological and socio-economic services that these species provide will be lost, potentially changing ecosystems irrevocably. We discuss options and current obstacles to achieving effective conservation, alongside consequences of failure to stem such anthropogenic mammalian extirpation. We propose a multi-pronged conservation strategy to help save threatened mammals from immediate extinction and avoid a collapse of food security for hundreds of millions of people.
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