Eco-crisis: The devastation of Borneo's forests

Warning: Do not look at this map if you don't want to feel depressed. 

The image shows how much of Borneo's biodiversity-rich forests have been destroyed or degraded in the last four decades -- and it's enough to ruin anybody's breakfast.

Trouble for orangutans and lots of other species  (from Mongabay)

Trouble for orangutans and lots of other species (from Mongabay)

From 1973 to 2010, the tropical rainforests of Borneo have been razed twice as fast as those elsewhere on the planet, according to a freely available study that just appeared in PLoS One.

In the paper, David Gaveau, Sean Sloan, and colleagues analyzed Landsat imagery to see how much of Borneo's mega-diversity forests have been cleared, burned, or degraded by industrial logging. 

It's not a pretty picture -- as also detailed here in the leading environmental website Mongabay.

In 1973, more than three-quarters of Borneo was blanketed by native forest, much of which was undisturbed or little disturbed, according to the study.

By 2010 nearly 17 million hectares of the forest -- an area larger than England, Wales, and Northern Ireland combined -- had vanished.

Echoing an earlier study that spanned all of Indonesia, industrial logging, oil palm, and wood-pulp plantations were apparently the biggest culprits, along with slash-and-burn farming.

Increasingly, large expanses of Borneo are dominated by selectively logged native forests.  As highlighted previously here at ALERT, these forests still retain considerable biodiversity and carbon, but are intensely vulnerable to being cleared or burned.

The challenge at hand for Borneo is clear, the study concludes.

It's vital to slow forest destruction, by safeguarding existing protected areas and especially by defending the selectively logged forests that now increasingly dominate the island.

 

We must save logged tropical forests

Four hundred million hectares--an area bigger than Mexico and Indonesia combined.  About the size of the Brazilian Amazon.

That's how much of the world's tropical forests are being selectively logged.  Unfortunately, these logged forests are intensely vulnerable to being cleared for oil palm, slash-and-burn farming, and other land-uses.

Logged forests... lots of biodiversity here

Logged forests... lots of biodiversity here

In the past, biologists have often emphasized the negative impacts of logging on biodiversity.  But a growing body of evidence shows that even heavily or repeatedly logged forests still retain most of their species and ecological functions. 

That's a vital conclusion because it underscores just how valuable these logged forests are

In a recent editorial, ALERT director Bill Laurance and his colleague David Edwards argue that protecting logged tropical forests should be very high on the agendas of conservationists.

With the rapid decline of old-growth tropical forests, retaining logged forests--and devising economically viable ways to manage them over the long term--are key priorities for the future.

 

The debate about forest conservation

In conservation practice, as in just about everything else, the pendulum of opinion swings back and forth. 

Right now, many ecologists are emphasizing the importance of conserving or rehabilitating forests that have been altered in various ways--such as selectively logged forests or secondary forests that are regenerating on formerly cleared land. 

Still valuable...  tiger footprint in a regenerating forest in Sumatra (photo by William Laurance).

Still valuable...  tiger footprint in a regenerating forest in Sumatra (photo by William Laurance).

One reason for this is that such modified habitats are so prevalent, and sometimes intensely vulnerable, across the planet.  For instance, around 400 million hectares of tropical forest globally is in some kind of logging estate.  Indonesia alone has at least 35 million hectares of selectively logged forest--an area larger than Germany--and much of this logged forest is unprotected and being cleared for agriculture. 

But there are also those who emphasize the values of old-growth forest.  One example is ALERT member Corey Bradshaw, who explains his views in this recent interview on Mongabay.

Bradshaw's views echo an analysis we published in Nature in 2011.  In that study, we found old-growth tropical forests had higher biodiversity-conservation values than all other modified forests or lands.  Nonetheless, native forest that had been selectively logged came in a close second, underscoring the importance of conserving these vulnerable forests.

In the end, no single conservation strategy always wins out.  All forests have value, and in many parts of the world, modified forests are just about all that remains.  That doesn't diminish the vital need to conserve old-growth forests wherever they still survive.

-Bill Laurance

Across the planet, big trees are in trouble

We all know that big animals such as elephants, rhinos and tigers are in trouble, but it turns out that the fate of our largest and oldest trees is just as dire.

Everywhere you look, big trees are hurting (photo by William Laurance)

Everywhere you look, big trees are hurting (photo by William Laurance)

All across the world, big trees are suffering.  They are being cleared for agriculture, felled by loggers, and are dying as a result of habitat fragmentation, exotic pests and pathogens, altered fire regimes, and severe droughts. 

Big trees are adapted for longevity and stability--two things in short supply in our rapidly changing world.

I first wrote about the dire fate of big trees in early 2012, in New Scientist.  That was followed by papers in Science in 2012 and Conservation Letters in 2013, in collaboration with leading ecologists David Lindenmayer and Jerry Franklin. 

Now there's more evidence of the vulnerability of big trees, from the Amazon.  Plinio Sist and colleagues have just found that many big trees are being damaged during selective logging operations there, and die soon afterward.  This is on top of the big trees that are actually being harvested.  The post-logging wave of tree death has a serious impact on the carbon storage and ecology of the forest.

It's increasing looking like big trees are an important barometer of Earth's environmental 'health'.

-Bill Laurance