Scientists in the Netherlands find a 70 per cent decline in mammal population in Western Africa, which is the biggest in the world
Industrial logging, urbanisation, agriculture, and infrastructure are all responsible for the increased degradation of tropical forests. Added to this is the hunting pressure which has affected more than half of them, according to a study.
The study claims that 52 per cent of the intact forests and 62 per cent of the wilderness areas are partially devoid of large mammals, and hunting may affect mammal populations in 20 per cent of protected areas in the tropics, particularly in West and Central Africa and Southeast Asia. The biggest declines were found in Western Africa, with more than 70 per cent of population reduction, while “most of the protected areas predicted to be at risk of defaunation are located in Benin, Burundi, Bangladesh, Thailand, and India,” read the paper published in PLOS Biology journal.
The study was conducted by Radboud University Nijmegen in the Netherlands. A team of scientists mapped the spatial patterns of mammal defaunation in the tropics using a database of 3,281 mammal abundance declines from local hunting studies between 1980 and 2017.
“Even forests that are considered intact according to satellite images – in which there is no visible deforestation or logging – could be partially defaunated,” said Ana Benítez-López from Radboud, in an article published on the university’s website.
The team estimated an average abundance decline of 13 per cent across all tropical mammal species, with medium-sized mammals, such as monkeys being reduced by 27 per cent and large mammals, like jaguars, leopards, elephants and rhinos by more than 40 per cent.
A previous study had revealed that bird populations declined on average by 58 per cent and mammal populations by 83 per cent in hunted forests, Environmental News Network (ENN) reported.
“Hunters target primarily large-bodied species because they provide relatively large meat yields and commercially valuable by-products such as horns and bones,” Benítez-López said.
“In addition, large mammals reproduce at slow rates, which means that it takes longer for their populations to recover when exploited,” she explained.
Besides hunting, habitat destruction and fragmentation by deforestation and logging are other causes of defaunation in tropical landscapes and may also have profound ramifications for ecosystem functioning. It can also affect the livelihoods of wild-meat-dependent communities.
"Hunting of carnivores may lead to an increase in herbivores with negative consequences for the vegetation whereas hunting of species that feed on fruits and disperse their seeds can have negative consequences on forest regeneration," Benítez-López said.
Lamenting that hunting effects were not considered much in large-scale biodiversity assessments, Benítez-López noted that the new study “may help fill this gap and eventually produce more representative estimates of human-induced biodiversity loss”.
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