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...

Humans are causing a massive animal extinction without precedent in 65 million years.

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

The disappearance of populations is a prelude to species extinction. No geographically explicit estimates have been made of current population losses of major indicator taxa. Here we compare historic and present distributions of 173 declining mammal species from six continents. These species have collectively lost over 50% of their historic range area, mostly where human activities are intensive. This implies a serious loss of ecosystem services and goods. It also signals a substantial threat to species diversity.

As human population and resource demands continue to grow, biodiversity conservation has never been more critical. About one-quarter of all mammals are in danger of extinction, and more than half of all mammal populations are in decline. A major priority for conservation science is to understand the ecological traits that predict extinction risk and the interactions among those predictors that make certain species more vulnerable than others. Here, using a new database of nearly 4,500 mammal species, we use decisiontree models to quantify the multiple interacting factors associated with extinction risk. We show that the correlates of extinction risk vary widely across mammals and that there are unique pathways to extinction for species with different lifestyles and combinations of traits. We find that risk is relative and that all kinds of mammals, across all body sizes, can be at risk depending on their specific ecologies. Our results increase the understanding of extinction processes, generate simple rules of thumb that identify species at greatest risk, and highlight the potential of decision-tree analyses to inform conservation efforts.conservation ͉ biodiversity ͉ body size ͉ IUCN Red List ͉ decision tree C ertain ecological traits, such as small geographic range, low population density, slow life history, and large body size are known to correlate strongly with extinction risk in mammals, and the importance of these traits can vary among different clades of mammals (1-5). Large body size, in particular, is a well-known predictor of both past and present human-related extinctions (4, 6, 7). Although the identification of these correlates of extinction has been an important first step in guiding conservation priorities, it is critical to understand how multiple ecological factors interact to predict risk across species that differ by orders of magnitude in body size, area of geographic range, abundance, life history, niche characteristics, and other traits. For example, it is not enough to know that species with small geographic ranges tend to be at greater risk; rather, we need to know how range size interacts with other ecological traits to make certain species with small ranges more vulnerable than others. By understanding how multiple key ecological predictors interact, we are able to identify the species at greatest risk and also to understand what makes them vulnerable. Additionally, to help avert the losses of populations and species of mammals (8-10), there is a real need for conservation scientists to provide results that are directly relevant and are easily interpretable for conservation practice. In this paper, we draw on a large dataset and methodological approach to build on current knowledge of extinction risk in mammals. Using a decision-tree modeling framework we (i) identify interactions among multiple ecological traits that lead to different pathways to extinction across mammals and (ii) use our model to codify simple rules of thumb that can be used to guide conservation.Decision-Tree Model...

The ongoing sixth mass species extinction is the result of the destruction of component populations leading to eventual extirpation of entire species. Populations and species extinctions have severe implications for society through the degradation of ecosystem services. Here we assess the extinction crisis from a different perspective. We examine 29,400 species of terrestrial vertebrates, and determine which are on the brink of extinction because they have fewer than 1,000 individuals. There are 515 species on the brink (1.7% of the evaluated vertebrates). Around 94% of the populations of 77 mammal and bird species on the brink have been lost in the last century. Assuming all species on the brink have similar trends, more than 237,000 populations of those species have vanished since 1900. We conclude the human-caused sixth mass extinction is likely accelerating for several reasons. First, many of the species that have been driven to the brink will likely become extinct soon. Second, the distribution of those species highly coincides with hundreds of other endangered species, surviving in regions with high human impacts, suggesting ongoing regional biodiversity collapses. Third, close ecological interactions of species on the brink tend to move other species toward annihilation when they disappear—extinction breeds extinctions. Finally, human pressures on the biosphere are growing rapidly, and a recent example is the current coronavirus disease 2019 (Covid-19) pandemic, linked to wildlife trade. Our results reemphasize the extreme urgency of taking much-expanded worldwide actions to save wild species and humanity’s crucial life-support systems from this existential threat.

Hotspots, which have played a central role in the selection of sites for reserves, require careful rethinking. We carried out a global examination of distributions of all nonmarine mammals to determine patterns of species richness, endemism, and endangerment, and to evaluate the degree of congruence among hotspots of these three measures of diversity in mammals. We then compare congruence of hotspots in two animal groups (mammals and birds) to assess the generality of these patterns. We defined hotspots as the richest 2.5% of cells in a global equal-area grid comparable to 1°l atitude ؋ 1°longitude. Hotspots of species richness, ''endemism,'' and extinction threat were noncongruent. Only 1% of cells and 16% of species were common to the three types of mammalian hotspots. Congruence increased with increases in both the geographic scope of the analysis and the percentage of cells defined as being hotspots. The within-mammal hotspot noncongruence was similar to the pattern recently found for birds. Thus, assigning global conservation priorities based on hotspots is at best a limited strategy.hotspot congruence ͉ birds ͉ patterns of species distribution ͉ endemism ͉ threatened species

The future of mammalian diversity in the tropics depends largely on the conservation value of human-dominated lands. We investigated the distribution of non-flying mammals in five habitats of southern Costa Rica: relatively extensive forest (227 ha), coffee plantation, pasture, coffee with adjacent forest remnant (<35 ha), and pasture with adjacent forest remnant (<35 ha). Of the 26 native species recorded in our study plots, 9 (35%) were restricted to forest habitat, 14 (54%) occurred in both forest and agricultural habitats, and 3 (11%) were found only in agricultural habitats. Species richness and composition varied significantly with habitat type but not with distance from the extensive forest. Interestingly, small forest remnants (<35 ha) contiguous with coffee plantations did not differ from more extensive forest in species richness and were richer than other agricultural habitat types. Small remnants contiguous with pasture were species-poor. When clearing started, the study region likely supported about 60 species. Since then, at least 6 species (10%), one family (4%), and one order (11%) have gone extinct locally. The species that disappeared were the largest in their families and included carnivorous (e.g., jaguar [Panthera onca]), herbivorous (e.g., Baird's tapir, [Tapirus bairdii]), and arboreal (e.g., mantled howler monkey [Alouatta palliata]) species. Although there is no substitute for native forest habitat, the majority of native, nonflying mammal species use countryside habitats. The populations of many persist even >5 km from relatively extensive forest, at least over the 40 years since forest clearance. Moreover, if hunting ceased, we expect that at least one of the locally extinct species could be reestablished in the existing landscape. Thus, there is an important opportunity to maintain and restore the diversity, abundance, and ecosystem roles of mammals in at least some human-dominated regions of the Neotropics. Biogeografía del Campo de Mamíferos Neotropicales: Oportunidades de Conservación en Paisajes Agrícolas de Costa Rica Resumen: El futuro de la diversidad de mamíferos en los trópicos depende principalmente del valor de la conservación de tierras dominadas por actividades humanos. Investigamos la distribución de mamíferos no voladores en cinco hábitats del sur de Costa Rica: selva relativamente extensa (227 ha), plantaciones de café, pastizal, café con remanente de selva adyacente (<35 ha) y pastizal con remanente de bosque adyacente (<35 ha). De las 26 especies nativas registradas en nuestras parcelas de estudio, 9 (35%) estaban restringidas al hábitat de bosque, 14 (54%) ocurrieron tanto en hábitats de bosque como agrícolas, y 3 (11%) solo se encontraron en hábitats agrícolas. La riqueza y composición de especies varió significativamente con el tipo de hábitat pero no con la distancia al bosque extenso. Lo interesante es que las, los remanentes pequeños de §Current address: Daily et al. Countryside Biogeography of Mammals 1815 bosque (<35 ha) contiguos a plantaciones de café no dif...