The TrickyScribe: Combined impact of rampant felling down of trees and wildlife exploitation on bird numbers is severely underestimated worldwide and could lead to the extinction of some endangered species, a joint study by National University of Singapore and the University of Sheffield has found.
Scientists focused on a hotspot of biodiversity in Southeast Asia, spanning Borneo, Sumatra, Java and Peninsular Malaysia, Sundaland, where habitat loss, poaching and wildlife trade are particularly intense.
A detailed study, conducted between October 2016 and July 2017, on as many as 308 forest-dependent bird species indicated that the loss of forest habitat and bird trapping in the area, in case examined together, resulted in a much higher average population loss than when accounted for separately. The study demands biodiversity to be considered in totality for effective measures to be implemented.
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The research also suggests that about 50 to 90 of forest-dependent species in the region including ruby-throated bulbul and white-crowned hornbill will most likely be extinct by the onset of the upcoming century.
Tropical forests are the most biodiverse ecosystems globally. Extensive loss of tropical forests, driven primarily by the expansion of agricultural land, however, threatens the survival of forest-dwelling species. That coupled with other anthropogenic disturbance such as logging, hunting and fires amplify the threat to biodiversity.
While the International Union for Conservation of Nature (IUCN) has been tracking the different forms of threats to wildlife, the assessments tend to look at each form of threat separately. These threats are, however, interconnected and the combined impact could be more severe than what currently estimated.
Recent extinctions of species like passenger pigeon and dodo, present common traits including a simultaneous combination of habitat loss and active hunting. This fatal combination of ingredients is present for scores of bird species in Sundaland. At present rates, vanishing forests and enormous trapping pressures are likely to drive many of them to extinction in the near future.
The said evaluation revealed that altogether 89 percent of the 308 forest-dependent bird species studied had experienced an average habitat loss of 16 percent due to deforestation; they also estimated that wildlife exploitation had led to a 37 percent decline in mean population on average.
Among the bird species studied, the researchers also identified 77 ‘commercially traded’ species that are exploited more often. They found that the estimated average decline for these species was 15.3 percent from deforestation alone, but when combined with the effects of exploitation, the estimated average decline was drastically increased to whopping 51.9 percent.
That apart, assessment of the combined impact of deforestation and exploitation in the study suggests that a total of 51 species should be listed as critically endangered, endangered or vulnerable – nearly doubling the number as listed by the IUCN now.
Without urgent policy level intervention to curb deforestation and slow the quantities of birds entering the cagebird trade, many species are likely to be lost in the near future. Failing to account for these combined threats can lead to a major underestimation of threats in the IUCN Red List assessments.
Combined impacts of deforestation, forest fragmentation and commercial exploitation are not unique to Southeast Asia. Rampant land-use change and wildlife trade drive the decline in parrots from Latin America, Africa and Asia earlier.