One of the largest area studies of forest loss impacting biodiversity shows that a third of the Amazon is headed toward or has just past a threshold of forest cover below which species loss is faster and more damaging. Researchers call for conservation policy to switch from targeting individual landowners to entire regions.

 

One of the first studies to map the impact of deforestation on biodiversity across entire regions of the Amazon has found a clear ‘threshold’ for forest cover below which species loss becomes more rapid and widespread.

 

By measuring the loss of a core tranche of dominant species of large and medium-sized mammals and birds, and using the results as a bellwether, the researchers found that for every 10% of forest loss, one to two major species are wiped out.

 

This is until the threshold of 43% of forest cover is reached, beyond which the rate of biodiversity loss jumps from between two to up to eight major species gone per 10% of disappeared forest.

 

While current Brazilian law requires individual landowners in the Amazon to retain 80% forest cover, this is rarely achieved or enforced. Researchers say that the focus should be shifted to maintaining 50% cover – just half the forest – but over entire landscapes rather than individual farms, in a bid to stop whole regions losing untold biodiversity by slipping below the 43% threshold at which species loss accelerates.

 

Unless urgent action is taken to stem deforestation in key areas that are heading towards or have just dipped below the forest cover ‘threshold’ – which, according to the research team’s models, amounts to a third of the Amazon – these areas will suffer the loss of between 31-44% of species by just 2030.

 

“These results support the need for a major shift in the scale at which environmental legislation is applied in Brazil and the tropics,” said Dr Jose Manuel Ochoa-Quintero, from Cambridge University’s Department of Zoology, who led the study, published recently in the journal Conservation Biology.

 

“We need to move from thinking in terms of compliance at a farm scale to compliance at a landscape scale if we are to save as many species as we can from extinction."

 

 

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