• Researchers studied the effects of gold mining on the Amazon rainforest
• Soil samples showed lower amounts of nitrogen in areas around mines
• They also found mercury levels that could be up 250 times higher than normal
• The effects of more mercury and less nitrogen kept new trees from growing 

Deforestation is threatening the Amazon rainforest both from above and below ground. 

A new study from researchers at the University of Leeds has found that gold mining in the Amazon leeches nutrients from the soil and pollutes the surrounding area with mercury.

According to the team, sites of former gold mines saw some of the lowest forest recovery rates ever recorded in rainforest terrain, and some former sites remained unable to grow new trees for up to four years after the mines closed.

A study of former gold mining sites in the Amazon rain forest found lowered amounts of nitrogen in the soil and higher concentrations of mercury from mining equipment runoff, which prevented new plants and trees from growing for years

'This study shows that tropical forests are strongly impacted by mining activities, and have very little capacity to re-establish themselves following mining,' University of Leeds's Michelle Kalamandeen told the university's news blog.

For the study, the team focused on an area called the Guiana Shield, where some 90% of the total deforestation in the Amazon has taken place.

The Guiana Shield spans Guyana, Suriname, French Guiana, Venezuela, parts, of Colombia, and parts of Brazil.

Deforestation related to mining in the Guiana Shield is responsible for the loss of more than two million tons of carbon stored in trees each year. 

In ground samples around former mining sites, the team found mercury concentrations that were up to 250 times higher than normal.

The team studied former mining sites in the Guiana Shield, a region of the Amazon spanning Guyana, Suriname, French Guiana, Venezuela, parts, of Colombia, and parts of Brazil

Grounds samples also had much lower amounts of nitrogen than normal, an important nutrient that helps fuel plant and tree growth.

'Not only does this have serious consequences for our battle against global warming by limiting Amazonian forests’ ability to capture and store carbon, but there is also a larger implication of contaminating food sources especially for indigenous and local communities who rely on rivers,' Kalamandeen said.

Mining operations currently affect more than 500,000 square miles of the Amazon, and the team called for better enforcement of laws protecting the rainforest and better safety standards for the mining industry.

In addition to inhibiting new tree growth, the team found mercury runoff from mining sites was a threat to local food and water supplies

'Active management and enforcement of laws is clearly needed to ensure recovery and to safeguard communities and there are methods available, such as replacing the soil using the overburdens at abandoned sites,' Kalamandeen said.

'But there is an urgent need for large-scale recovery management to be tested and implemented.'

'We could be facing a race against the clock.'

MAP REVEALS THE DEVASTATING RATE OF DEFORESTATION AROUND THE GLOBE

Using Landsat imagery and cloud computing, researchers mapped forest cover worldwide as well as forest loss and gain. Over 12 years, 888,000 square miles (2.3 million square kilometers) of forest were lost, and 309,000 square miles (800,000 square kilomet

The destruction caused by deforestation, wildfires and storms on our planet have been revealed in unprecedented detail.

High-resolution maps released by Google show how global forests experienced an overall loss of 1.5 million sq km during 2000-2012.

For comparison, that’s a loss of forested land equal in size to the entire state of Alaska.

The maps, created by a team involving Nasa, Google and the University of Maryland researchers, used images from the Landsat satellite.

Each pixel in a Landsat image showing an area about the size of a baseball diamond, providing enough data to zoom in on a local region.

Before this, country-to-country comparisons of forestry data were not possible at this level of accuracy.

‘When you put together datasets that employ different methods and definitions, it's hard to synthesise,’ said Matthew Hansen at the University of Maryland.