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 n the island of Borneo, the world's second largest
tropical rain forest is dying. Its death will mean the disappearance
of a unique ecosystem where trees time their reproduction to
match the periodic arrival of El Niño. Loss of the forest
also could have a global financial impact, since timber exports
contribute as much as $8 billion annually to the Indonesian economy
and provide 80 percent of plywood used in the US home construction
industry.
 According
to a study published in the Dec. 10 issue of Science by
an international research team led by U-M tropical ecologist
Lisa M. Curran, this ecological and economic resource is being
destroyed by human activity, which has intensified the effects
of regional climate change.
From 1985
to 1999, Curran and her colleagues studied dipterocarpaca
the main family of rain forest canopy trees in Indonesian Borneo.
Field research covered a 57-square-mile area, but focused on
six square miles in the Gunung Palung National Park. The research
team also surveyed timber concessions throughout the surrounding
province of West Kalimantan and studied 30 years of export records
to determine the impact of logging in the region and on the park.
Curran's study
is the first to document an ecosystem with a rare reproductive
strategy called masting. More than 50 different species of Bornean
dipterocarp trees synchronize their reproduction limiting
fruit and seed production to brief, intense periods. Curran discovered
that these bursts of reproduction are initiated by the arrival
of the El Niño Southern Oscillation or ENSO, a periodic
shift in tropical Pacific circulation patterns that brings drought
to Indonesia.
"We recorded
four masting episodes from 1986 to 1999 with an average interval
of 3.7 years," said Curran, an assistant professor of tropical
ecology at the U-M. "With the possible exception of one
very minor event in 1994, they all occurred during ENSO years.
Climatic conditions of an El Niño year trigger simultaneous
fruiting in dipterocarps, and are essential for regional seed
production."
According
to Curran, masting gives canopy trees an important survival advantage.
In a typical six-week masting period, her research team collected
180 pounds of seed -- ranging in size from a chestnut to a pistachio
nut -- from every acre of the six-square-mile survey area on
the forest floor.
"It's
like Thanksgiving in the forest," Curran said. Wild boar,
orangutans, parakeets, jungle fowl, partridges, and other animals
congregate to stuff themselves. Local villagers collect baskets
of seeds called illipe nuts to sell as a cash crop. Because so
much seed is produced simultaneously over such a large area,
however, there is still enough leftover to germinate and produce
a carpet of new seedlings on the forest floor.
In the Science
article, Curran and her co-researchers describe how the forest
in Gunung Palung is changing following a decade of intensive
dipterocarp logging in huge timber concessions surrounding the
park. From 1991 to 1998, production of mature, viable dipterocarp
seed fell from 175 pounds per acre (196 kilograms per hectare)
to 16.5 pounds per acre (18.5 kilograms per hectare). Despite
a major fruiting event during the 1998 El Niño year, no
new dipterocarp seedlings were found in the survey area.
"Even
though the park is supposedly off-limits to logging, the forest
is losing the ability to regenerate itself," Curran said.
Because seed predators can't find food outside the park, they
move inside to eat the dipterocarp seeds before they germinate,
according to Curran. Massive forest fires on nearby logging plantations,
which destroyed an area the size or Denmark or Costa Rica in
1997-98, brought pollution and intensified El Niño's drought
killing the few remaining dipterocarp seedlings.
"It's
very sad, but unless the Indonesian government implements sustainable
forestry practices, creates financial incentives to harvest responsibly,
and prevents clearing and burning for industrial plantations,
this ecosystem will be unable to recover," Curran said.
"The real injustice here is to the Indonesian people in
Kalimantan, because the majority depend on the forest for their
basic livelihood. They will bear the environmental and socioeconomic
costs, but the benefits from this harvest went to a few timber
tycoons."
The research
was supported by the US Agency for International Development,
National Science Foundation, U-M, International Timber Trade
Organization, Wildlife Conservation Society, World Wide Fund
for Nature, Conservation International, W. Alton Jones Foundation,
National Geographic Society, and the Conservation, Food and Health
Foundation.
Collaborators
in the research study include Gary Paoli, U-M graduate student;
Izefri Caniago, from the US Agency for International Development
in West Kalimantan; Dwi Astianti, from the University of Tanjungpura
in West Kalimantan; Monika Kusneti, from the World Wide Fund
for Nature; Mark Leighton of Harvard University; C. Endah Nirarita,
from Wetlands International in Indonesia; and Herman Haeruman
from the Indonesian National Development Planning Agency. 
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