Momentous changes ahead for the tropics

The world's tropical regions will be the epicenter of change in global economies, population growth, and environment.  That's the take-home message of a groundbreaking report that forecasts massive changes this century in the tropics.

Huge changes ahead...  (from Mongabay)

Huge changes ahead... (from Mongabay)

The ambitious State of the Tropics Report was launched last week in Burma and Singapore, in a special televised event. 

The report was kicked off by Nobel Laureate and Burmese leader Aung San Suu Kyi with assistance from Sandra Harding, the Vice-Chancellor of James Cook University in Australia, and a panel of experts that included ALERT director Bill Laurance

Produced by a coalition of 12 universities and research institutes from the Asia-Pacific, Africa, and Latin America, the State of the Tropics report sees dramatic changes ahead for the world's tropical regions:

- by the latter part of this century, the population of tropical nations will swell by over 3 billion additional people, with Africa's population nearly quadrupling

- food demand in tropical and developing nations will double by mid-century

- by 2050, two-thirds of all children will live in the tropics

- land-use pressures will intensify sharply because of a dire need to increase food and biofuel production in the tropics

- as the century unfolds, tropical nations will increasingly be the centers of global economic growth and also rising geopolitical conflicts over land, water, and natural resources

- the tropics sustains 80% of all species, many of which will be imperiled by rising habitat loss, climate change, and other perils.

The State of the Tropics report is the first comprehensive effort to project change across the entire tropical region -- which will increasingly become a key driver of social, economic, and environmental change globally.

 

Rainforests imperiled by environmental 'one-two punch'

A strange thing is happening in the Amazon.  So strange that scientists who've spent 35 years studying the rainforests there are still scratching their heads about it.

Forests behaving in very peculiar ways  (photo by R. O. Bierregaard)

Forests behaving in very peculiar ways (photo by R. O. Bierregaard)

In the heart of the Amazon, one of the world's largest and longest-running ecological experiments has uncovered evidence that the remote forests there are being altered by an environmental 'one-two punch' -- a combination of threats acting in concert. 

One of these threats is obvious.  The experiment -- known as the Biological Dynamics of Forest Fragments Project -- has chopped up the rainforest into isolated patches surrounded by cattle ranches.  A large team of researchers has been studying how the trees, vines, mammals, birds, and other animals of the rainforest respond to the environmental insult of fragmentation.

But something decidedly unexpected has also been happening.  The forests are changing in ways far beyond what you'd expect fragmentation to cause.  The dynamics of the forest -- the rates at which trees grow and die -- has accelerated, and disturbance-loving vines are proliferating.  Even undisturbed forests are changing too.

What's happening?  The best explanation is that the forests are responding to rising carbon dioxide levels in the atmosphere -- the result of billions of tons of human-caused carbon emissions each year.  Plants use carbon dioxide for photosynthesis, and when the gas increases it evidently alters forest dynamics and plant communities.

Vines like both forest disturbance and rising carbon dioxide  (photo by William Laurance)

Vines like both forest disturbance and rising carbon dioxide (photo by William Laurance)

So, Amazonian forests are not just being affected by local land-use threats such as habitat fragmentation, but also by global-scale changes in the atmosphere -- an environmental 'one-two punch'. 

This finding was just reported in a paper led by ALERT director Bill Laurance and co-authored by ALERT members Philip Fearnside and Tom Lovejoy, the latter of whom founded the Amazon fragmentation project 35 years ago.

The bottom line: Humans are changing the world in myriad ways, and these changes can interact in a complex fashion.  As a result, it could be very difficult to predict the fate of many ecosystems in the future.

 

Are vines taking over the world?

Most types of vines like forest disturbances, so it's not very surprising to see vines proliferating in logged, fragmented and regenerating forests.  And in warmer parts of the world, many introduced vine species are proliferating; the aggressive kudzu vine, for instance, has rapidly colonized much of the southeastern US.

But it's less apparent why vines should be increasing in intact, undisturbed forests.  That is precisely what researchers are now finding, across a number of sites in the tropics.  In a recently accepted paper in Ecology, for instance, my colleagues and I found that woody vines (lianas) have increased by about 1% per year over the last 14 years in old-growth rainforests in central Amazonia.

Why are vines on the rise?  In our paper we consider some of the leading hypotheses for this puzzling environmental mystery.

-Bill Laurance

Woody vines (lianas) and trees are ancient enemies.  

Woody vines (lianas) and trees are ancient enemies.