Gold mining limits Amazon rainforest recovery

Gold mining significantly limits the regrowth of Amazon forests, which in turn greatly reduces their ability to accumulate carbon, according to a new study. The researchers warn that the impacts of mining on tropical forests are long-lasting and that active land management and restoration will be necessary to recover tropical forests on previously mined lands. 

Gold mining has rapidly increased across the Amazon in recent years, especially along the Guiana Shield, where it is responsible for as much as 90% of total deforestation. The Shield encompasses Guyana, Suriname, French Guiana, Venezuela and small parts of Colombia and northern Brazil, and its forests hold roughly twenty billion tonnes of aboveground carbon in its trees, according to a statement from the University of Leeds.

An international study led by the University of Leeds is the first to provide detailed field-based information on the regeneration of forests in Guyana after gold mining, and the first ground-based estimate of carbon sink lost as a result of gold mining activities across the Amazon.

The team’s findings show that forest recovery rates on abandoned mining pits and tailing ponds are amongst the lowest ever recorded for tropical forests. At some sites there was nearly no tree regeneration even after three to four years since mining had stopped.

They estimate that mining-related deforestation results in the annual loss of over two million tons of forest carbon across the Amazon. The lack of forest regrowth observed following mining suggests that this lost carbon cannot be recovered through natural regeneration.

Lead author Dr Michelle Kalamandeen said in the statement: “This study shows that tropical forests are strongly impacted by mining activities, and have very little capacity to re-establish themselves following mining.

“Our results clearly show the extraction process has stripped nitrogen from the soil, a critical component to forest recovery, and in many cases directly contributed to the presence of mercury within neighbouring forests and rivers. Active mining sites had on average 250 times more mercury concentrations than abandoned sites.”

The team used forest inventory plots installed on recently abandoned mines in two major mining regions in Guyana, and re-censused the sites 18 months later. The study analysed soil samples and determined individual trees’ above-ground biomass – the tree’s living plant material – to determine recovery and chemical changes caused by mining.

Their results suggest that forest recovery is more strongly limited by severe mining-induced depletion of soil nutrients, especially nitrogen, rather than by mercury contamination. The high rate of mercury does however have serious implications for negative impacts on food security, water supply and local biodiversity.

Photo credit: Andre Deak, flickr/Creative Commons

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