Global gold rush is killing the world's rainforests

After a short holiday-season hiatus, ALERT is now back in action.  Here, we examine the alarming impact that illegal gold-mining is having on rainforest environments around the world.

Moonscape... aftermath of illegal gold mining in Sumatra, Indonesia  (photo by William Laurance )

Moonscape... aftermath of illegal gold mining in Sumatra, Indonesia (photo by William Laurance)

The rise in illegal gold mining has two main causes.  First, the price of gold is skyrocketing, in part because investors see it as a safeguard against unstable economic conditions.  Second, new roads are proliferating across the tropics, opening up once-remote areas to invasions of illegal miners.

For example, a recent study by Nora Alvarez-Berríos and Mitch Aide documents the escalation of illegal gold mining in South America.  They found that gold mining has accelerated significantly since 2OO7, following a rush by investors to find havens for their money following the global financial crisis.

Mining can have huge impacts in certain areas.  Alvarez-Berríos and Aide found that mining was especially severe in four general regions of South America: the Guianas, the Southwest Amazon, the Tapajós–Xingú area of the western Amazon, and the Magdalena Valley in the Colombian Andes.  This shocking video shows just how badly miners are decimating the Southwest Amazon in Peru following construction of the Inter-oceanic Highway there.

Around 17O,OOO hectares of forest was destroyed outright in these four regions, but even worse was the broader-scale impacts on aquatic ecosystems and water quality.  Gold miners cause enormous siltation of streams and rivers as well as water pollution by toxic mercury, which they use to separate gold from river sediments. 

Gold miners also often have conflicts with local indigenous groups and poach wildlife.  For instance, armed miners in French Guiana murdered two park guards there, who were attempting to defend the park.

The scourge of illegal gold mining is by no means limited to Latin America.  It is escalating rapidly across vast expanses of Africa, Asia, and many other regions of the tropics. 

It's become stylish to talk about 'blood diamonds', but let there be no mistake -- 'blood gold' is even more environmentally deadly and is a growing threat to the world's rainforests.

 

A new Armageddon for amphibians?

Amphibians -- such as frogs, toads, salamanders, newts, and caecilians -- are among the most ancient of all terrestrial vertebrates.  And increasingly, they seem to be among the most imperiled as well.

Biodiversity in retreat...  many frogs are imperiled  (photo by Mike Trenerry)

Biodiversity in retreat...  many frogs are imperiled (photo by Mike Trenerry)

Why?  For one thing, amphibians, more than any other group of terrestrial vertebrates, rely intimately on water.  Their eggs dry out on land, and their larvae (such as tadpoles) are often aquatic.  Across the planet, aquatic ecosystems are being destroyed and degraded -- by pollution, dams, river channelization, introduced predators and competitors, and other maladies -- at a horrific pace.

Beyond this, amphibians seem unusually vulnerable to exotic diseases.  The water that they rely on so intimately is an excellent medium for transmitting pathogens, many of which will quickly die if they dry out. 

Many amphibians need clean water for survival  (photo by William Laurance)

Many amphibians need clean water for survival (photo by William Laurance)

Combine that trait with our hyper-mobile modern society -- where exotic organisms are suddenly being moved across the planet at lightening speed, often by accident -- and you have the makings of environmental Armageddon.

For example, a few decades ago a mysterious chytrid fungus suddenly appeared and swept like a tsunami across Australia, Latin America, and parts of Asia and Europe with deadly effect. 

In total, some 200 species of frogs and salamanders have declined catastrophically or been driven to global extinction by the fungal disease (notably, ALERT director Bill Laurance and colleagues did some of the earliest work on the pathogen's impacts).  

Now, there is a new disease threat.  Exotic viruses have appeared that seem to be targeting a range of amphibian species.  This is frightening, because viruses are usually specific to a particular species

A virus that can attack several species at once could be catastrophic for amphibians.  Normally, a virus dies out when it kills most individuals of its host species, because the host becomes so rare that the virus is no longer transmitted successfully.

But a multi-species virus is different.  One of its host species might be largely wiped out, but the virus can still thrive in a different species.  Because it persists in the environment, even when one of its hosts becomes perilously rare, such a virus can drive a species completely to extinction.

That is exactly what seems to be happening now in Europe.  At least two new types of Ranaviruses are plaguing frogs and salamanders there, causing massive die-offs in several different species of hosts at once. 

The viruses induce hemorrhaging in the frogs, creating open sores and killing their limb tissues.

Alarmingly, even reptiles might be affected; a snake that ate an infected salamander died soon afterward, apparently from the virus. 

Such events suggest that one of the most damaging features of modern humanity might be our proclivity for moving exotic organisms all around the planet.  Species have adapted to ecosystems in which a major new pathogen might come along once every few centuries or millennia.  Now they're arriving at a pace that's blindingly faster than that.

Little wonder that the amphibians -- among the most ancient denizens of the Earth -- are having a hard time surviving the onslaught.