Page 350 - Environment: The Science Behind the Stories

100 more resilient to fragmentation. For the create an immense amount of edge.
Forest Amazon as a whole, it suggested that A satellite image study in the 1990s
isolated
80 regrowing forest (as opposed to pasture) estimated that for every 2 acres of
into
fragment can buffer fragments against some spe- land deforested, 3 acres were brought
60
Species 40 The secondary forest habitat also BDFFP scientists emphasize that
cies loss.
within 1 km of a road or pasture edge.
introduced new species—generalists
adapted to disturbed areas. Frogs, leaf- impacts across the Amazon will be
more severe than the impacts revealed
20 cutter ants, and small mammals and by their experiments. This is because
birds that thrive in second-growth soon most real-life fragments (1) are not
0
1980 1985 1990 1995 became common in adjacent fragments. protected from hunting, logging, mining,
Year Open-country butterfly species moved and fires; (2) do not have secondary
FIGURE 2 Species richness of understory in, displacing interior-forest butterflies. forest to provide connectivity; (3) are not
birds declined in this 1-ha forest plot The invasion of open-country spe- near large tracts of continuous forest
after it was isolated as a fragment in cies illustrated one type of edge effect. that provide recolonizing species and
1984. Data from Ferraz, G., et al., 2003. Rates There were more: Edges receive more maintain humidity and rainfall; and
of species loss from Amazonian forest fragments. sunlight, heat, and wind than interior (4) are not square in shape, and thus
Proc. Natl. Acad. Sci. 100: 14069–14073. © 2003 forest, which can kill trees adapted feature more edge. Scientists say the
National Academy of Sciences. By permission. to the dark, moist interior. Tree death years of data argue for preserving
On average, about how many bird results in the flux of carbon dioxide numerous tracts of Amazonian forest
species were present in this forest to the atmosphere, which worsens that are as large as possible.
plot before fragmentation? How many climate change. Sunlight also promotes The BDFFP has inspired another
were present after fragmentation? growth of vines and shrubs that cre- large-scale, long-term study, this one
ate a thick, tangled understory along located in Borneo. The Stability of
less like islands—but it led to new edges. As BDFFP researchers docu- Altered Forest Ecosystems (SAFE)
insights. Researchers learned that this mented these impacts, they found that project is documenting changes that
habitat can act as a corridor for some many edge effects extended far into take place in tropical forests as they
species, allowing them to disperse from the forest (FIGURE 3). Small fragments are logged and converted to oil palm
mature forest and recolonize frag- essentially became “all edge.” plantations. This project, underway
ments from which they’d disappeared. The results on edge effects are for just a few years, should shortly be
By documenting which species did relevant for all of Amazonia, because providing data and insights that may
this, scientists learned which might be forest clearance and road construction help us conserve biodiversity amid
the rush to oil palm plantations in
Southeast Asia.
Increased wind disturbance Ironically, today the BDFFP study
Elevated tree mortality
Invasion of disturbance-adapted butterflies site is itself threatened by forest
fragmentation. A Brazilian govern-
Altered species composition of leaf-litter invertebrates
Edge effect Lower relative humidity ment agency has settled colonists just CHAPTER 12 • FOREST S, FOREST MAN A GEMENT, AND PR O TECTED AREAS
Reduced canopy height
outside the site and has proposed
Reduced soil moisture
Increased air temperature settling 180 families inside it. Develop-
ment is proceeding up a new highway
Reduced understory-bird abundance
Increased sunlight from Manaus, a city of 1.7 million
Invasion of disturbance-adapted plants people, to Venezuela, and wherever
roads are built and people settle,
0 100 200 300 400 500 600 logging, hunting, mining, and burning
Edge penetration distance (m) follow. BDFFP researchers can now
FIGURE 3 Many edge effects documented by the BDFFP extend far into the interior of hear chainsaws and shotgun blasts
forest fragments. Data from studies summarized in Laurance, W.F., et al., 2002. Ecosystem decay of from their study plots. “It would be
Amazonian forest fragments: A 22-year investigation. Conservation Biology 16: 605–618, Fig 3, adapted. tragic,” says leading BDFFP scientist
Reprinted by permission of John Wiley & Sons, Inc. William Laurance, “to see a site that’s
given us so much information be lost
Would a tree inside a forest fragment, 275 meters in from the edge, be
susceptible to any edge effects? If so, which ones? so easily.”

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