There are jungles as full of trees as empty animals. The hunt’s almost done with them. A thorough review of studies on the impact of hunting activities on the biodiversity of tropical forests shows that where hunters arrive, the abundance of animal life has been reduced by up to 90%. The higher or less proximity to human settlements or a road determines whether a jungle will be empty of life.
The study, conducted by a group of ecologists led by Spanish researcher Ana Benítez, has reviewed 175 previous types of research conducted since 1970 that analyzed the effects of hunting on the abundance of wildlife. The other essential information they were looking for ways to measure the range in kilometers of the effect, as far as the hunters’ impact reached. They obtained data on 254 species of mammals and 97 species of birds. The work includes the situation of the rainforests of Latin America, Central, and Southeast Asia, and other tropical biomes, such as the African savannah or the Amazon closed.
Overall, in hunting areas, the abundance of birds has been reduced by 58% on average and that of mammals by 83% compared to areas where hunters do not arrive. These are averages; there are regions and species where biodiversity has disappeared by up to 90%. For researchers, the percentage difference between birds and mammals may be due to the relatively larger size of the seconds, which makes them more interesting pieces either to eat them or to sell them.
“Commercial hunting has more impact than subsistence, especially among mammals,” says Benitez, a researcher at Radboud University in Nimega, Netherlands. Although it might seem from the type of meat (from monkeys to rodents) that it is a small-scale local trade, Benitez also highlights its international dimension: “In some cases, they see this meat as a deli, in others, as is the case with pangolin in China, its drama is due to traditional medicine.”
The other great data offered by this research published in Science is the relationship between distance and degree of biodiversity reduction. Researchers applied the logic: the impact should be higher the closer to humans. They identified two key starting points, human settlements, and roads. They found that hunters only stray from the village or the street if strictly necessary.
Thus, they estimated that within a radius of about 500 meters around one of these personal hotspots, there are hardly any birds. In the case of mammals, 90% have disappeared in 700 meters around. But as the distance from the center increases, the fauna also recovers. The abundance of birds is equal between hunting areas and hunter-free areas upon reaching seven kilometers. Mammals need about 40 kilometers to escape the hunters.
“These distances are related to the access capacity of a walking person,” says the Spanish researcher. But it’s not a static distance. “As the larger animals disappear, or the ones with the most commercial value, the hunter increases the distance he travels,” adds Benítez.
In addition to the proximity to a village or a road, the study also highlights that the closer to a city, it can function as a market, the worse for animals. Also, it reveals that species living in protected areas are also not spared from harassment by hunters. In this case, hunting is almost all commercial in nature.
Although the aim of this work was not to identify which species are the most hunted, the researchers were able to draw some conclusions: the largest animals are the most decimated. Among mammals, while the various species of ungulates, rodents, and apes are hunted mainly for their meat, felines are exterminated by being competitors of humans.
What is worse is that, as the study authors point out, the impact of hunting on animal life will be increasing. The two main risk factors are proximity to a village or road. “In Africa, 90% of the remaining forests are less than 50 km from a road,” Benítez recalls. With the expected increase in population in these regions, the new settlements, the new roads will go further and with them the hunters.
In a commentary on Science, the biologists of the University of California, Berkeley, Justin Brashares, and Kaitlyn Gaynor, recall that hunting is a very complex problem: In these regions, hunting overlaps to survive with hunting to make some money and with the illegal one that offers more significant benefits. And, in many cases, it is the same hunter in all three cases.