Effects of Subsistence Hunting on Vertebrate Community Structure in Amazonian Forests

TLDR

Subsistence hunting impacts large areas of tropical forest, yet distinguishing hunted from non‑hunted sites is difficult because it leaves few visible signs. The study aimed to assess how subsistence hunting alters vertebrate community structure across 25 Amazonian forest sites with varying hunting pressure. Using standardized line‑transect censuses over ten years, the authors quantified vertebrate biomass, abundance, and size‑class composition to evaluate hunting effects. The analysis revealed that hunting pressure sharply reduces vertebrate biomass—dropping from ~1200 kg km⁻² in non‑hunted sites to <200 kg km⁻² in heavily hunted ones—especially diminishing large‑bodied species, while overall density remains unchanged; floodplain forests maintain higher game biomass, and the estimated 23.5 million game vertebrates harvested annually (≈89 t of bushmeat, worth US$190 million) underscores the substantial socioeconomic value and the need to account for forest type and productivity in management.

Abstract

Abstract: Subsistence hunting affects vast tracts of tropical wilderness that otherwise remain structurally unaltered, yet distinguishing hunted from nonhunted tropical forests presents a difficult problem because this diffuse form of resource extraction leaves few visible signs of its occurrence. I used a standardized series of line‐transect censuses conducted over a 10‐year period to examine the effects of subsistence game harvest on the structure of vertebrate communities in 25 Amazonian forest sites subjected to varying levels of hunting pressure. Crude vertebrate biomass, which was highly correlated with hunting pressure, gradually declined from nearly 1200 kg km −2 at nonhunted sites to less than 200 kg km −2 at heavily hunted sites. Hunting had a negative effect on the total biomass and relative abundance of vertebrate species in different size classes at these forest sites, but it did not affect their overall density. In particular, persistent hunting markedly reduced the density of large‐bodied game species (&gt;5 kg), which contributed a large proportion of the overall community biomass at nonhunted sites (65–78%) and lightly hunted sites (55–71%). Nutrient‐rich floodplain forests contained a consistently greater game biomass than nutrient‐poor unflooded forests, once I controlled for the effects of hunting pressure. Conservative estimates of game yields indicate that as many as 23.5 million game vertebrates, equivalent to 89,224 tons of bushmeat with a market value of US$190.7 million, are consumed each year by the rural population of Brazilian Amazonia, which illustrates the enormous socioeconomic value of game resources in the region. My cross‐site comparison documents the staggering effect of subsistence hunters on tropical forest vertebrate communities and highlights the importance of considering forest types and forest productivity in game management programs.