shows that keeping more fish in the sea
may give an ecosystem some protection
against unwanted algae.
Biologists have warned that burgeoning algae, encouraged by excess nutrients in the water, ranks as one of the
most serious threats to the Baltic Sea. To
see if the region’s declines in perch and
other predatory fish also encourage algal
outbreaks, Britas Klemens Eriksson of
the University of Groningen in Haren,
the Netherlands, and his colleagues set
up field experiments. Keeping top predators away from study plots began a cascade of changes that eventually led to
fewer small creatures grazing on algae.
“Not all species are created exactly
equal,” says Boris Worm of Dalhousie
University in Halifax, Canada. If a top
predator disappears, change can shoot
through an ecosystem. “It’s like hitting a
node in a power grid — and the lights go
out everywhere,” he says.
Worm’s own work suggests that fisheries in the more species-rich of the world’s
marine ecosystems appear less likely to
collapse and faster to recover than fisher-
Population declines in European birds
120
Index (set at 100 in 1980)
110
100
90
80
70
60
50
1980 1985
Common forest birds
(33 species)
Common farmland birds
( 19 species)
1990 1995
Year
2000 2003
Close-up on birds scientists have been
tracking declines in bird populations around
the globe for decades. Eriocnemis isabellae,
native to colombia, has recently been labeled
critically endangered by the iUcn.
soUrce: convention on biological Diversity
ies in species-poor regions. The analysis,
based on more than 50 years of data from
the Food and Agriculture Organization
of the United Nations, was published in
Science in 2006.
Even genetic variation within the same
species has been shown to affect how well
ecosystems pull up their socks and repair
themselves. Jay Stachowicz of the University of California, Davis remembers a
New Year’s Eve call from his then-student
Randall Hughes. Brant geese had found
Hughes’ study plots of eelgrass clones,
which she had genetically analyzed with
great care. And the geese had eaten just
about all of the eelgrass.
WHAT TO DO: Prioritize wild spaces
reversing the downward spiral of biodiversity will take more
than protecting wild places, but that’s where scientists are
starting. Declaring protected zones across a range of terrestrial ecosystems is the one area where clear progress toward
saving biodiversity has been made, says an upcoming United
nations report. now researchers are making strategic picks
for sheltered zones to fill in the gaps on land and in the sea.
Just documenting diversity doesn’t guarantee that a place
becomes a park. selecting good bits requires understanding
how critters use space and weighing competing claims for it.
one recent approach looks to double the punch of the
case for setting aside land by identifying biodiverse places
that also provide documented ecosystem services, says
taylor ricketts, who heads the World Wildlife fund’s conser-
vation science program, based in Washington, D.c. though
the two don’t match tidily, ricketts has found a few natural
sweet spots important for their variety of living things and for
such boons as storing abundant carbon or collecting water.
the natural capital project, based at stanford University, is
refining software to allow fine-scale analyses, and tanzania,
the state of Hawaii and others are already using the software.
to pick worthy spots, scientists must also understand how
protectees use space, a big puzzle in the seas. selecting a
reef (papaha
_
naumokua
_
kea marine reserve shown), requires
knowledge of where the juvenile fish and corals that popu-
late those waters traveled from.
a modeling technique that includes ocean currents can
give a broad picture of dispersing sea creatures, says eric
treml of the University of Queensland in st. lucia, australia. the technique predicts that coral larvae in the pacific
travel some 50 to 150 kilometers before settling in. of
particular interest to conservationists, treml says, might be
reefs that serve as stepping-stones for surfing corals and
reef clusters that are especially isolated. — Susan Milius
