“In human-dominated landscapes, intensive hunting interacts synergistically with forest fragmentation to further threaten wildlife populations.”

Using a meta-analysis of 82 studies on 254 mammal and 1,640 bird species, we assess the effects of three major regional-scale drivers of tropical defaunation, namely hunting, forest degradation and forest conversion, on measures of abundance. ... Our findings suggest that hunting, forest degradation and conversion have marked but varied defaunation impacts on mammal and bird communities of relatively intact tropical forests. For mammal abundances, all three disturbance types exerted a negative effect, while the response in birds was more mixed. Hunting had stronger negative impacts than forest degradation or conversion on mammal abundances across all species.

Intensive bushmeat hunting has led to widespread defaunation of tropical forests, particularly of large mammals and birds. In many tropical regions, hunting pressure is highest in forests close to human settlements, roads and other infrastructure. ... When combined with habitat fragmentation from logging, agriculture and infrastructure development, hunting can result in 'empty forests' where the vegetation remains but wildlife populations are severely depleted, undermining ecosystem functions and services.

Using multiple indicators, including the Living Planet Index and Red List Index, we show that global biodiversity has continued to decline despite the expansion of protected areas. Major drivers include habitat loss and fragmentation, overexploitation (including hunting), pollution, invasive species and climate change. ... In many human-dominated landscapes, these drivers co-occur and may interact, but our analyses at global scale do not resolve the specific interaction terms between hunting pressure and forest fragmentation.

The project summary explains: "Tropical mammals have lost on average 40% of their original distribution due to the combined effect of hunting pressure and human land use." It further notes that "land-use change (deforestation, agriculture, infrastructure) and hunting interact to reduce the remaining suitable habitat and accessible populations, especially in human-dominated landscapes." The work emphasises that considering only one pressure underestimates overall threat levels.

This theoretical study focuses on fragmentation per se and species richness, without incorporating hunting. The authors summarize: “Habitat loss is one of the key drivers of the ongoing decline of biodiversity… When the total amount of habitat is large, fragmentation per se tends to increase species diversity, but if the total amount of habitat is small, the situation is reversed: fragmentation per se decreases species diversity.” The paper notes that fragmentation has complex, context-dependent effects, but does not address interactive or synergistic effects with hunting.

We provide empirical evidence that hunting pressure interacts with forest disturbance in a non-additive way. Vertebrate populations in disturbed and fragmented forests subject to intensive hunting showed much higher levels of depletion than would be expected from the independent effects of disturbance or hunting alone.

Here, we assess whether and how habitat area, fragmentation, and hunting can synergistically affect the extinction risk of Neotropical primates. Our results show that hunting substantially increases extinction risk in fragmented landscapes, and that the interaction between hunting pressure and reduced habitat area is synergistic rather than additive for many species.

PBL summarises a Science study: "Hunting accounts for 83 and 58% declines in tropical mammal and bird populations." The article notes that there are "several drivers of animal decline in tropical landscapes: habitat destruction, overhunting, fragmentation etcetera" and that hunting pressure is higher in areas accessible by roads and settlements. It highlights that hunting, when combined with land-use change and fragmentation, can drastically reduce wildlife populations across human-dominated tropical landscapes.

We used spatially explicit population models to investigate how different forms of human land use interact with species traits. Fragmentation from roads, agriculture and development reduced population viability, but the magnitude of these effects depended strongly on dispersal ability and initial population size, indicating that responses to fragmentation are highly context dependent.

Population declines of many avian species are often attributed to increased rates of nest predation in fragmented landscapes, yet mechanisms underlying these effects have rarely been examined. We reviewed the literature to determine the extent to which hypotheses about nest predators and fragmentation have been invoked and compared this to the number of direct tests of predators with respect to habitat edge, patch size, or landscape type. ... There were seven studies (22 tests) in which different extents of fragmentation were compared... Nest predators were significantly more abundant in areas with increasing fragmentation in only 4 (18%) tests... An increased number of predators in fragmented landscapes was generally attributed to increased food availability and mesopredator release.

IUCN notes that "over-harvesting of wildlife for meat, in combination with habitat loss and fragmentation, is leading to widespread defaunation in many tropical forests." It explains that logging roads and other infrastructure "open up previously remote areas to hunters" and that in such human-dominated landscapes "the combined effects of habitat fragmentation and intensive hunting can drive rapid declines and local extinctions of large-bodied species."

Fragmentation is problematic because it diminishes both habitat size and connectivity among individuals and populations. In general, there is a direct relationship between increased fragmentation of forests and decreased biodiversity. Many species have difficulty flourishing or surviving in these modified environments of reduced size, increased isolation, and new ecological boundaries.

Discussing human-dominated fragmented landscapes, IFAW states: “Habitat fragmentation negatively impacts wildlife and biodiversity… According to research published in 2025, fragmented landscapes have 12.1% fewer species than those that aren’t fragmented.” The article also notes that fragmentation can increase exposure to human threats: “When animals are pushed into smaller and smaller pockets of habitat, they may be forced to roam into human settlements… This can lead to crop raiding and livestock predation, and can threaten human safety.” Hunting is mentioned generically as one of several human threats but the piece does not present quantitative evidence for synergistic interactions between hunting and fragmentation.

The study reports that subsistence game hunting has profound negative effects on the species diversity, standing biomass, and size structure of vertebrate assemblages. It further notes that these impacts are exacerbated in fragmented forests, where hunting and reduced habitat area act together to increase local extinction risks.

The article describes forest fragmentation as "a hidden but powerful driver of ecological disruption and biodiversity loss" and states that "animals have a difficult time moving throughout the forest areas due to fragmentation that splits the once-unified woodlands into distinct ecosystems." It notes that human activities such as roads and slash-and-burn agriculture in the Amazon create isolated patches and that "wildlife, especially those in the understory, suffers greatly from rainforest splits" and isolation of animal groups. Hunting is mentioned among human pressures that increase when forests are opened up, compounding the negative effects on wildlife.

This review of animal welfare impacts in fragmented, human-dominated landscapes states that welfare effects fall into categories including “direct effects, such as injury, death, or increased predation; [and] population-level effects, such as changes in population size and structure.” It explains that “patch size, characteristics of the matrix, and resources remaining in the new, smaller patch interact with the traits of a given species to define the population effects.” Hunting is briefly listed among human pressures in fragmented habitats, but the article does not provide evidence that hunting and fragmentation act synergistically to threaten wildlife beyond their individual impacts.

The piece explains that "a habitat with more edges will increase the likelihood of animals leaving the habitat and entering a landscape that is outside their typical range." It notes that "the edge effect increases the mortality rate of animals due to either the lack of food in the area or poses a higher chance of animals being hunted by other predators." As an example, it cites mountain caribou, where "as a result of habitat fragmentation, predation on caribou by wolves climbed, facilitated by an open space." While this case refers to predation rather than human hunting, it illustrates how fragmentation can interact with killing pressure to exacerbate population declines.

This teaching document summarizes key mechanisms of habitat fragmentation: “fragmentation on habitat pattern: (a) reduction in habitat amount, (b) increase in number of habitat patches, (c) decrease in sizes of habitat patches, and (d) increase in isolation of patches. These four effects form the basis of most quantitative measures of habitat fragmentation.” It synthesizes empirical work showing that mean patch size affects species richness and extinction rates, but does not directly address how intensive hunting in human-dominated landscapes might interact synergistically with fragmentation.

Across the conservation biology literature, many case studies from tropical forests report that overhunting in fragmented habitats leads to "empty forest" syndromes where large vertebrates are disproportionately lost. However, meta-analyses and modelling studies note that the strength and direction of the interaction between hunting and fragmentation can vary; in some systems the effects appear roughly additive, while in others clear synergistic, more-than-additive impacts on extinction risk are reported.