CLIMATE CHANGE: Tropical Forests Fight for Survival

  • by Stephen Leahy* - Tierramérica (uxbridge, canada)
  • Wednesday, January 28, 2009
  • Inter Press Service

However, some experts say widespread planting of previously logged forests offers hope for preserving some of the region's rich and unique biodiversity.

Recent satellite data have shown that about 350,000 square kilometres of the original forested areas are growing back, Greg Asner of the Washington-based Carnegie Institution said at the Smithsonian symposium Jan. 12 at the Smithsonian National Museum of Natural History, also in the U.S. capital.

That is only 1.7 percent of the immense planetary belt of original forest that once covered 20 million square kilometres. Twelve million sq km have already been cleared while another five million have been selectively logged, Asner reported.

'There is going to be lots of tropical forest left in the future but it will be different forest,' says Joseph Wright of the Smithsonian Tropical Research Institute (STRI) in Panama.

Marginal farmland is being abandoned in the tropics and there is also a large-scale migration of people from rural areas into cities.

'The key question is, what is the conservation value of this land?' Wright told Tierramérica from Washington. 'I think there will be a high level of biodiversity.'

Tropical rainforests are estimated to contain 80 percent the planet's terrestrial biodiversity. They also produce 20 to 30 percent of the world’s oxygen and are part of the planet's climate regulating system.

Ira Rubinoff, STRI director emeritus, wonders if the new second-growth forest can provide a home to millions of unique tropical species and the same ecosystem services.

'These are not trivial questions. The services tropical forests provide are extremely important for the entire planet,' Rubinoff told Tierramérica.

'We don't know the answers. We know more about the moon than the Amazon forest,' he added.

If second-growth forests are connected to primary old growth forests, then species might be able to move into them. And the regrowth areas would also have to be large enough and be undisturbed for many decades to provide good quality habitat, speculates Eldredge Bermingham, director and senior staff scientist at STRI.

Many other factors are at play, including soil quality, changes in precipitation and wind patterns, and hunting pressures.

'STRI has a new study to look at the regrowth of 650 hectares of old pasture land along the Panama Canal in hopes of answering some of these questions,' he said. However, the study will have to run 25 years.

By human-time scales, tropical forests are ancient.

'There are lots of trees 500 to 1,500 years old in primary forests,' said William Laurance, an STRI researcher and chair of the Smithsonian symposium.

While secondary and degraded forests are better than pasture lands, they will sustain only a fraction of existing animal species, Laurance told Tierramérica in an interview from Panama City.

'In biodiversity terms, this is akin to a barn door closing after the horses have escaped,' he said.

Secondary forests are also far more prone to fires than primary forests, which are more humid, he says.

Moreover, the current drivers of deforestation - logging, mining, industrial agriculture including biofuels - are unlikely to leave second-growth forests untouched.

The deforestation of irreplaceable old growth forests is happening faster than any time in history. Indonesia is losing more than two million hectares of forest per year and Borneo is being devastated, according to Laurance.

On the other side of the planet, the world's second largest rainforest, in the Democratic Republic of the Congo, is being carved up. 'China is busy buying every stick of timber,' he said. 'The world now loses the equivalent of 50 football fields of old-growth forest every minute.'

But what really worries Laurance is climate change. Tropical plants and animals have evolved under very stable climatic conditions and they cannot tolerate wide ranges in temperatures like species in temperature regions, he explained.

'An increase of two degrees Celsius is enough to wipe out some species,' he said.

Heat waves have already led to recent species extinctions, he said. Three years ago a heat wave in Australia's tropical forest was believed to have caused the extinction of the white lemuroid possum. More recently, thousands of flying foxes died when temperatures reached 40 degrees C in the same region, he said.

Wright agrees that climate change is a 'huge problem' for the biodiversity of tropical regions. The vast majority of tropical forests exist where the annual average temperature is 25 to 26C.

Before the end of this century, temperatures in tropical regions are projected to be 3C higher.

No forests exist today where the annual average temperature is 28C, Wright says. 'That doesn't mean something else won't replace tropical forests, but we don't know what it will be.'

Protecting forests from climate change means preserving existing primary forests, says Laurance.

'We're hopeful this symposium will bring the importance of protecting tropical forests to the attention of Obama,' the new U.S. president, he added.

The United States needs to play a significant role in the carbon market and help countries like Brazil and Indonesia understand that they could receive a lot of money through that mechanism, he stressed.

(*This story was originally published by Latin American newspapers that are part of the Tierramérica network. Tierramérica is a specialised news service produced by IPS with the backing of the United Nations Development Programme, United Nations Environment Programme and the World Bank.)

© Inter Press Service (2009) — All Rights ReservedOriginal source: Inter Press Service

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