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Tropical forests are increasingly degraded by industrial logging, urbanization, agriculture, and infrastructure, with only 20% of the remaining area considered intact. However, this figure does not include other, more cryptic but pervasive forms of degradation, such as overhunting. Here, we quantified and mapped the spatial patterns of mammal defaunation in the tropics using a database of 3,281 mammal abundance declines from local hunting studies. We simultaneously accounted for population abundance declines and the probability of local extirpation of a population as a function of several predictors related to human accessibility to remote areas and species' vulnerability to hunting. We estimated an average abundance decline of 13% across all tropical mammal species, with medium-sized species being reduced by >27% and large mammals by >40%. Mammal populations are predicted to be partially defaunated (i.e., declines of 10%-100%) in ca. 50% of the pantropical forest area (14 million km2), with large declines (>70%) in West Africa. According to our projections, 52% of the intact forests (IFs) and 62% of the wilderness areas (WAs) are partially devoid of large mammals, and hunting may affect mammal populations in 20% of protected areas (PAs) in the tropics, particularly in West and Central Africa and Southeast Asia. The pervasive effects of overhunting on tropical mammal populations may have profound ramifications for ecosystem functioning and the livelihoods of wild-meat-dependent communities, and underscore that forest coverage alone is not necessarily indicative of ecosystem intactness. We call for a systematic consideration of hunting effects in (large-scale) biodiversity assessments for more representative estimates of human-induced biodiversity loss.

A global zoning scheme is proposed to limit the environmental costs of road building while maximizing its benefits for human development, by discriminating among areas where road building would have high environmental costs but relatively low agricultural advantage, areas where strategic road improvements could promote agricultural production with relatively modest environmental costs, and ‘conflict areas’ where road building may have large agricultural benefits but also high environmental costs. The number and extent of roads will expand dramatically this century 1 . Globally, at least 25 million kilometres of new roads are anticipated by 2050; a 60% increase in the total length of roads over that in 2010. Nine-tenths of all road construction is expected to occur in developing nations 1 , including many regions that sustain exceptional biodiversity and vital ecosystem services. Roads penetrating into wilderness or frontier areas are a major proximate driver of habitat loss and fragmentation, wildfires, overhunting and other environmental degradation, often with irreversible impacts on ecosystems 2 , 3 , 4 , 5 . Unfortunately, much road proliferation is chaotic or poorly planned 3 , 4 , 6 , and the rate of expansion is so great that it often overwhelms the capacity of environmental planners and managers 2 , 3 , 4 , 5 , 6 , 7 . Here we present a global scheme for prioritizing road building. This large-scale zoning plan seeks to limit the environmental costs of road expansion while maximizing its benefits for human development, by helping to increase agricultural production, which is an urgent priority given that global food demand could double by mid-century 8 , 9 . Our analysis identifies areas with high environmental values where future road building should be avoided if possible, areas where strategic road improvements could promote agricultural development with relatively modest environmental costs, and ‘conflict areas’ where road building could have sizeable benefits for agriculture but with serious environmental damage. Our plan provides a template for proactively zoning and prioritizing roads during the most explosive era of road expansion in human history.

Assessment of the impact of armed conflict on large herbivores in Africa between 1946 and 2010 reveals that high conflict frequency is an important predictor of wildlife population declines. African wildlife compromised by conflict The effect of armed conflict on wildlife populations is debated. Joshua Daskin and Robert Pringle assess the impact of armed conflict on 253 populations of large herbivores in protected areas across Africa, using data collected between 1946 and 2010. Armed conflict affected more than 70% of the studied areas over this period, with population growth rates decreasing with increased conflict frequency—the single most important predictor of wildlife population trends. The researchers suggest that sustained conservation efforts in conflict zones and rapid interventions following ceasefires could help to safeguard many at-risk populations and species. Large-mammal populations are ecological linchpins 1 , and their worldwide decline 2 and extinction 3 disrupts many ecosystem functions and services 4 . Reversal of this trend will require an understanding of the determinants of population decline, to enable more accurate predictions of when and where collapses will occur and to guide the development of effective conservation and restoration policies 2 , 5 . Many correlates of large-mammal declines are known, including low reproductive rates, overhunting, and habitat destruction 2 , 6 , 7 . However, persistent uncertainty about the effects of one widespread factor—armed conflict—complicates conservation-planning and priority-setting efforts 5 , 8 . Case studies have revealed that conflict can have either positive or negative local impacts on wildlife 8 , 9 , 10 , but the direction and magnitude of its net effect over large spatiotemporal scales have not previously been quantified 5 . Here we show that conflict frequency predicts the occurrence and severity of population declines among wild large herbivores in African protected areas from 1946 to 2010. Conflict was extensive during this period, occurring in 71% of protected areas, and conflict frequency was the single most important predictor of wildlife population trends among the variables that we analysed. Population trajectories were stable in peacetime, fell significantly below replacement with only slight increases in conflict frequency (one conflict-year per two-to-five decades), and were almost invariably negative in high-conflict sites, both in the full 65-year dataset and in an analysis restricted to recent decades (1989–2010). Yet total population collapse was infrequent, indicating that war-torn faunas can often recover. Human population density was also correlated (positively) with wildlife population trajectories in recent years; however, we found no significant effect, in either timespan, of species body mass, protected-area size, conflict intensity (human fatalities), drought frequency, presence of extractable mineral resources, or various metrics of development and governance. Our results suggest that sustained conservation activity in conflict zones—and rapid interventions following ceasefires—may help to save many at-risk populations and species.

The arrival of modern humans into previously unoccupied island ecosystems is closely linked to widespread extinction, and a key reason cited for Pleistocene megafauna extinction is anthropogenic overhunting. A common assumption based on late Holocene records is that humans always negatively impact insular biotas, which requires an extrapolation of recent human behavior and technology into the archaeological past. Hominins have been on islands since at least the early Pleistocene and Homo sapiens for at least 50 thousand y (ka). Over such lengthy intervals it is scarcely surprising that significant evolutionary, behavioral, and cultural changes occurred. However, the deep-time link between human arrival and island extinctions has never been explored globally. Here, we examine archaeological and paleontological records of all Pleistocene islands with a documented hominin presence to examine whether humans have always been destructive agents. We show that extinctions at a global level cannot be associated with Pleistocene hominin arrival based on current data and are difficult to disentangle from records of environmental change. It is not until the Holocene that large-scale changes in technology, dispersal, demography, and human behavior visibly affect island ecosystems. The extinction acceleration we are currently experiencing is thus not inherent but rather part of a more recent cultural complex.

The disappearance of many North American megafauna at the end of the Pleistocene is a contentious topic. While the proposed causes for megafaunal extinction are varied, most researchers fall into three broad camps emphasizing human overhunting, climate change, or some combination of the two. Understanding the cause of megafaunal extinctions requires the analysis of through-time relationships between climate change and megafauna and human population dynamics. To do so, many researchers have used summed probability density functions (SPDFs) as a proxy for through-time fluctuations in human and megafauna population sizes. SPDFs, however, conflate process variation with the chronological uncertainty inherent in radiocarbon dates. Recently, a new Bayesian regression technique was developed that overcomes this problem—Radiocarbon-dated Event-Count (REC) Modelling. Here we employ REC models to test whether declines in North American megafauna species could be best explained by climate changes, increases in human population densities, or both, using the largest available database of megafauna and human radiocarbon dates. Our results suggest that there is currently no evidence for a persistent through-time relationship between human and megafauna population levels in North America. There is, however, evidence that decreases in global temperature correlated with megafauna population declines. There are a number of competing explanations for the late Pleistocene extinction of many North American megafauna species. Here, the authors apply a Bayesian regression approach that finds greater concordance between megafaunal declines and climate change than with human population growth.

Although deforestation and forest degradation have long been considered the most significant threats to tropical biodiversity, across Southeast Asia (Northeast India, Indochina, Sundaland, Philippines) substantial areas of natural habitat have few wild animals (>1 kg), bar a few hunting-tolerant species. To document hunting impacts on vertebrate populations regionally, we conducted an extensive literature review, including papers in local journals and reports of governmental and nongovernmental agencies. Evidence from multiple sites indicated animal populations declined precipitously across the region since approximately 1980, and many species are now extirpated from substantial portions of their former ranges. Hunting is by far the greatest immediate threat to the survival of most of the region's endangered vertebrates. Causes of recent overhunting include improved access to forests and markets, improved hunting technology, and escalating demand for wild meat, wildlife-derived medicinal products, and wild animals as pets. Although hunters often take common species, such as pigs or rats, for their own consumption, they take rarer species opportunistically and sell surplus meat and commercially valuable products. There is also widespread targeted hunting of high-value species. Consequently, as currently practiced, hunting cannot be considered sustainable anywhere in the region, and in most places enforcement of protected-area and protected-species legislation is weak. The international community's focus on cross-border trade fails to address overexploitation of wildlife because hunting and the sale of wild meat is largely a local issue and most of the harvest is consumed in villages, rural towns, and nearby cities. In addition to improved enforcement, efforts to engage hunters and manage wildlife populations through sustainable hunting practices are urgently needed. Unless there is a step change in efforts to reduce wildlife exploitation to sustainable levels, the region will likely lose most of its iconic species, and many others besides, within the next few years. Aunque la deforestación y la degradación de los bosques han sido consideradas durante largo tiempo como las amenazas más significativas para la biodiversidad tropical, a lo largo del sureste asiático (noreste de India, Indochina, Sondalandia, Filipinas) hay áreas sustanciales de hábitat natural que tienen algunos animales silvestres (>1 kg), excluyendo a algunas especies tolerantes a la caza. Para documentar los impactos regionales de la caza sobre las poblaciones de vertebrados realizamos una revisión extensiva de la literatura, incluyendo artículos de revistas locales y reportes de agencias gubernamentales y no gubernamentales. La evidencia de los múltiples sitios indicó que las poblaciones animales declinaron precipitosamente en la región desde aproximadamente 1980 y que muchas especies ahora están extirpadas de porciones sustanciales de sus extensiones previas. La caza es por mucho la mayor amenaza inmediata para la supervivencia de la mayoría de los vertebrados en peligro de la región. Las causas del exceso reciente de caza incluyen el acceso mejorado a los bosques y a los mercados, tecnología mejorada de caza, productos medicinales derivados de la vida silvestre y los animales silvestres como mascotas. Aunque los cazadores generalmente toman a especies comunes, como los cerdos y las ratas, para su propio consumo, también toman especies raras de manera oportuna y venden la carne excedente y los productos de valor comercial. También existe una extensa caza enfocada en especies de alto valor. En consecuencia, como es practicada actualmente, la caza no puede considerarse sustentable en ningún lugar de la región y en la mayoría de las localidades la aplicación de la legislación de áreas y especies protegidas es débil. El enfoque de la comunidad internacional sobre el mercado transfronterizo falla en abordar la sobreexplotación de la vida silvestre porque la caza y la venta de la carne salvaje son en general un asunto local y la mayoría es consumida en las aldeas, pueblos rurales y ciudades cercanas. Además de una aplicación mejorada, los esfuerzos por involucrar a los cazadores y por manejar las poblaciones de vida silvestre por medio de prácticas de caza sustentable son una necesidad urgente. A menos que haya un cambio de paso en los esfuerzos por reducir la explotación de la vida silvestre a niveles sustentables, la región probablemente pierda la mayoría de sus especies icónicas, además de muchas otras, en el transcurso de los próximos años.

Large, fruit-eating vertebrates have been lost from many of the world’s ecosystems. The ecological consequences of this defaunation can be severe, but the evolutionary consequences are nearly unknown because it remains unclear whether frugivores exert strong selection on fruit traits. I assessed the macroevolution of fruit traits in response to variation in the diversity and size of seed-dispersing vertebrates. Across the Indo-Malay Archipelago, many of the same plant lineages have been exposed to very different assemblages of seed-dispersing vertebrates. Phylogenetic analysis of >400 plant species in 41 genera and five families revealed that average fruit size tracks the taxonomic and functional diversity of frugivorous birds and mammals. Fruit sizewas 40.2–46.5% smaller in the Moluccas and Sulawesi (respectively), with relatively depauperate assemblages of mostly small-bodied animals, than in the Sunda Region (Borneo, Sumatra, and Peninsular Malaysia), with a highly diverse suite of large and small animals. Fruit color, however, was unrelated to vertebrate diversity or to the representation of birds versus mammals in the frugivore assemblage. Overhunting of large animals, nearly ubiquitous in tropical forests, could strongly alter selection pressures on plants, resulting in widespread, although trait-specific, morphologic changes.

Habitat destruction and overhunting are two major drivers of mammal population declines and extinctions in tropical forests. The construction of roads can be a catalyst for these two threats. In Southeast Asia, the impacts of roads on mammals have not been well-documented at a regional scale. Before evidence-based conservation strategies can be developed to minimize the threat of roads to endangered mammals within this region, we first need to locate where and how roads are contributing to the conversion of their habitats and illegal hunting in each country. We interviewed 36 experts involved in mammal research from seven Southeast Asian countries to identify roads that are contributing the most, in their opinion, to habitat conversion and illegal hunting. Our experts highlighted 16 existing and eight planned roads - these potentially threaten 21% of the 117 endangered terrestrial mammals in those countries. Apart from gathering qualitative evidence from the literature to assess their claims, we demonstrate how species-distribution models, satellite imagery and animal-sign surveys can be used to provide quantitative evidence of roads causing impacts by (1) cutting through habitats where endangered mammals are likely to occur, (2) intensifying forest conversion, and (3) contributing to illegal hunting and wildlife trade. To our knowledge, ours is the first study to identify specific roads threatening endangered mammals in Southeast Asia. Further through highlighting the impacts of roads, we propose 10 measures to limit road impacts in the region.

Many vertebrate species undergo population fluctuations that may be random or regularly cyclic in nature. Vertebrate population cycles in northern latitudes are driven by both endogenous and exogenous factors. Suggested causes of mysterious disappearances documented for populations of the Neotropical, herd-forming, white-lipped peccary ( Tayassu pecari , henceforth “WLP”) include large-scale movements, overhunting, extreme floods, or disease outbreaks. By analyzing 43 disappearance events across the Neotropics and 88 years of commercial and subsistence harvest data for the Amazon, we show that WLP disappearances are widespread and occur regularly and at large spatiotemporal scales throughout the species’ range. We present evidence that the disappearances represent 7–12-year troughs in 20–30-year WLP population cycles occurring synchronously at regional and perhaps continent-wide spatial scales as large as 10,000–5 million km 2 . This may represent the first documented case of natural population cyclicity in a Neotropical mammal. Because WLP populations often increase dramatically prior to a disappearance, we posit that their population cycles result from over-compensatory, density-dependent mortality. Our data also suggest that the increase phase of a WLP cycle is partly dependent on recolonization from proximal, unfragmented and undisturbed forests. This highlights the importance of very large, continuous natural areas that enable source-sink population dynamics and ensure re-colonization and local population persistence in time and space.

1. Demography and conservation status of many wild organisms are increasingly shaped by interactions with humans. This is particularly the case for large, wide-ranging carnivores. 2. Using 206 mortality records (1999-2012) of lions in Hwange National Park, Zimbabwe, we calculated mortality rates for each source of anthropogenic mortality, modelled risk of anthropogenic mortality across the landscape accounting for time lions spent in different parts of the landscape, and assessed whether subsets of the population were more at risk. 3. Anthropogenic activities caused 88% of male and 67% of female mortalities; male mortality being dominated by trophy hunting while the sources for female mortality were more varied (bycatch snaring, retaliatory killing, hunting). 4. Landscapes of anthropogenic mortality risk revealed that communal subsistence farming areas, characterized by high risk (due to retaliatory killing) but avoided by lions, are population sinks. Trophy hunting areas and areas within protected areas bordering communal farmland, where bushmeat snaring is prevalent, form 'ecological traps' (or 'attractive sinks'). 5. Lions avoided risky areas, suggesting they may make behavioural decisions based on perceptions of risk. Experienced adults used risky areas less and incorporated lower proportions of them in their home ranges than young individuals, suggesting that the latter may either be naïve or forced into peripheral habitats. 6. Synthesis and applications. This paper contributes to an understanding of how large carnivore populations are affected by anthropogenic mortality across the conservation landscape. This is critical to designing focussed, appropriate and cost-effective conservation management strategies. Agricultural areas are intuitively identified by conservationists as being risky for carnivores due to retaliatory killing, with threats largely mitigated against by improving livestock protection. However, parts of protected areas may also form less easily identified 'attractive sinks' for carnivores. In particular, trophy hunting areas adjacent to national parks need careful management to avoid damaging effects of overhunting. Law enforcement is needed to reduce the effects of bushmeat poaching on predators and other wildlife in protected areas. To be most effective, resource-limited antipoaching activities should prioritize wildlife-rich areas close to human settlement as these tend to be hot spots for bushmeat poaching.