SCIENCE sciencemag.org 2 OCTOBER 2020 • VOL 370 ISSUE 6512 19dangered Kangaroo Island glossy black
cockatoo after 75% of its habitat burned.
But observers have seen large flocks move
to unburned areas of the island, says
Karleah Berris of Natural Resources Kanga-
roo Island. And many of the birds appear
to have bred and fledged young. “It seems
they are coping with the reduction in food
by [moving] to where the food is,” she says.
Researchers were also worried about the
Kangaroo Island dunnart, a shrew-size car-
nivorous marsupial. Even before the fires,
just 500 or so remained, and they lost 95%
of their habitat to the flames. But auto-
mated cameras have revealed that at least
some dunnarts survived, and managers
moved quickly to build fences to protect the
remaining animals from feral cats.
Other findings are more ominous. In New
South Wales, fires killed about one-third
of the state’s koalas, a government inquiry
found in July. It warned that the marsupial
would be extinct in the state by 2050 if dra-
matic measures are not taken to conserve it.
And in the state’s Nightcap National Park,
a survey found that fires destroyed 10% or
more of the remaining stands of several criti-
cally endangered rainforest trees. Some spe-
cies were down to fewer than 200 trees before
the fires, says botanist Robert Kooyman
of Macquarie University; they are now “cer-
tainly a few steps closer to extinction.”
Such concerns have prompted scientists
to ask Australia’s government to expand its
endangered species list. At least 41 verte-
brates that were not endangered before the
fires now face existential threats, Woinarski
and others reported in July in Nature
Ecology & Evolution. An additional 21, al-
ready tagged as threatened, might need
greater protection. Marsh has recom-
mended adding 16 invertebrate species
found on Kangaroo Island to the list, in-
cluding the assassin spider. “That species is
really hanging in the balance,” she says.
In the United States, researchers say it’s
too soon to know how many species the
fires have put in jeopardy. But there are
already worrying reports. In Washington,
biologists estimate the fires have killed 50%
of the state’s endangered pygmy rabbits,
which inhabit sagebrush flats that burned
this year. They believe only about 50 of
North America’s smallest rabbit remain. Of-
ficials estimate the flames have also killed
30% to 70% of the state’s sage grouse and
sharp-tailed grouse, birds that also depend
on sagebrush.
In California, the impact of fires in 2014
may offer a preview. After flames swept
through habitat of the endangered spot-
ted owl, many of the birds abandoned
nesting sites, biologists Gavin Jones of
the U.S. Forest Service’s Rocky MountainResearch Station and M. Zachariah Peery
from the University of Wisconsin (UW),
Madison, found. In 2015, some 22% of nest-
ing sites used by the birds in 2014 were not
reoccupied and still are empty, Jones says,
and this year’s fires could add to the losses.
Western fires also threaten the white-
headed woodpecker, found only in pine
forests in the Pacific Northwest and Califor-
nia, and the Grace’s warbler, limited to pine
and oak forests in the southwestern United
States and northern Mexico, says wild-
life biologist Vicki Saab, also at the Rocky
Mountain Research Station.
Plants that have small ranges and are
found in burned areas, such as the Coulter
pine in California, might also face trouble,
says Camille Stevens-Rumann, a fire eco-
logist at Colorado State University, Fort
Collins. “California especially has a lot of
endemic plant species that could be very
much impacted,” she says.
The longer term consequences for eco-
systems are harder to predict, research-
ers say. In both Australia and the Western
United States, many ecosystems are adapted
to fire and even require it to thrive. “Many
of the old-growth forests we know and love
in the Pacific Northwest were born of large
and severe fires centuries ago,” says Brian
Harvey, a wildfire ecologist at the Univer-
sity of Washington, Seattle. Fires can also
help create a mosaic of habitats that sup-
port a wealth of species, he and others note.
But climate change adds to the
uncertainty about how forests will respond
this time. “The postfire climate is likely to be
warmer and drier than when the parent trees
established long ago,” Harvey says, making it
harder for ecosystems to recover, and bod-
ing more fire in the future. “Just a little more
drought can lead to much bigger fires,” says
Monica Turner, a fire ecologist at UW who
calls climate change “a threat multiplier.”
Already, some ecosystems in North Amer-
ica that have had frequent or intense burns
are not regenerating. In some places, such
as the sagebrush ecosystem of the Great
Basin west of the Sierra Nevada mountain
range and forests in the Klamath Mountains
along the California-Oregon border, invasive
shrubs or grasses appear to have taken over.
Because the invaders burn frequently, they
appear to be preventing seedlings from ma-
turing. In Australia, researchers have similar
concerns. In the state of Victoria, forests of
alpine ash, a towering eucalyptus tree found
in moist regions, historically experienced
fires less than once a century or so. Now,
some forests have been hit by five fires in the
past 20 years, and scientists fear some of the
stately groves will disappear for good. jJohn Pickrell is a journalist in Sydney.T
he placenta—a Frisbee-size hunk of
tissue that chaperones a fetus in the
uterus only to be tossed aside in the
delivery room—has mysterious begin-
nings. The organ emerges from cells
that develop alongside the embryo,
and that have been difficult to grow in the lab.
Now, researchers have devised a way to de-
rive and observe early precursors of placental
cells in a dish. They have found a method of
“reprogramming” adult cells, reverting themto a primitive state, that can prompt them to
become trophoblast stem cells (TSCs), which
give rise to placental cells.
The method promises a window on how
defects in placental development may lead
to infertility, miscarriage, and preeclampsia,
a dangerous complication of pregnancy. “It’s
like gaining a toehold on Mars,” says repro-
ductive biologist Susan Fisher at the Univer-
sity of California, San Francisco. “We know
almost nothing about the early steps.”
Those steps begin just days after a sperm
and egg join. “The first decision in human
life is to set aside the placental, supportiveStem cell
studies probe
origins of
the placenta
Lab models of organ will
track how it emerges—and
what can go wrong
DEVELOPMENTAL BIOLOGYBy Kelly ServickThe outer layer of cells (thin ring above) in a several-
days-old human embryo goes on to form the placenta.IMAGE: ANDY WALKER/MIDLAND FERTILITY SERVICES/SCIENCE SOURCE