are to use protected areas to maintain large contiguous natural areas with only limited human
impact; to achieve representative coverage of
habitats and species currently at high risk (48);
and to secure key areas for provision of ecosystem
Conservation science is a mature discipline
armed with knowledge and tools for effective
management of populations and habitats. For
example, analysis of the IUCN Red List showed
that although the threat status of birds and
mammals worsened over the two decades prior to
2008 (Fig. 1D), without recent conservation actions
the situation would now be 18% worse still (Fig. 3,
A and B) (50). In western Europe, the millennia-long decline of large-bodied vertebrates has at
last been turned around, as populations of large
carnivores recover and large herbivores return to
habitats from which they have been long absent.
This is due to a combination of factors, including nature policy and legislation of the European
Union, improved public attitudes, and rewilding
of abandoned agricultural landscapes (51, 52).
These successes have come from management
of high-priority species and landscapes. Tackling
overexploitation and habitat loss over large regions
is more difficult, but there have been successes.
In waters of the United States and the northeast
Atlantic, many large, highly managed fisheries
have undergone reductions in fishing pressure
and consequent increases in biomass since the
1990s (53). Attention is now turning to interventions such as catch shares and comanagement
arrangements (54) to improve smaller, unassessed
fisheries common in developing countries. More
generally, community-based conservation (CBC)
projects, which engage communities as stakeholders
and devolve control over natural resources to them
while improving access to benefits from sustainable
use, show promise in reducing overexploitation
and improving livelihoods (55).
Deforestation in the Brazilian Amazon has
been reduced to around one-third of its peak in
2004, despite a recent spike (56). This was evidently due to many factors, including expansion
of protected areas, improved enforcement of forest-protection codes and incentives for compliance
with those codes, intensification of production of
beef and soy on already cleared areas, and market
embargoes against product from newly cleared
lands (57). Production of soy and beef continued
to grow as deforestation fell after 2005, and the
retention of forest avoided the emission of 3.2 Gt
of CO2 and should confer other benefits, including stabilization of river discharge and reduced
risk of inhibition of rainfall, as well as retained
Efforts to sustain biodiversity in farmed land-
scapes have produced mixed results (58, 59). Con-
servation measures on farmland are often costly,
and although some succeed, they typically reduce
farm yields and hence are likely to displace pro-
duction elsewhere (60). This has led instead to
calls for land-sparing: increasing yields on exist-
ing farmland in order to reduce pressure on re-
maining habitats and, in some instances, enable
habitat restoration (60). If they are not simply to
catalyze further agricultural expansion, land-sparing
interventions need mechanisms that directly couple
yield growth with habitat protection (61). Such ini-
tiatives would also be facilitated by explicit land-use
zoning to distinguish areas where production is
intensified and others to be spared.
One of our greatest immediate challenges is
to minimize the impacts of new infrastructure
development, especially in hotspots of biodiversity
in the developing world. Large infrastructure
projects are potentially damaging for two reasons.
First, some projects have massive direct effects
on entire ecosystems. For example, the Three
Gorges Dam on the Yangtze River in China is
disrupting the ecology of a region with 177 en-
demic fish species (62). Loss of top carnivores
such as the Yangtze river dolphin Lipotes vexillifer
and Chinese paddlefish Psephurus gladius is an
early sign of ecosystem collapse (63), as is the
decline in number of fish species recorded at
Dongting Lake downstream of the dam, where
species richness fell from 85 in 2003 to 66 in
2014, only 2 years after completion of the dam
Second, development of infrastructure frequently catalyzes many other threats and thereby
triggers rapid escalation of total pressure on biodiversity. The scale of new developments is colossal. For example, 334 new hydropower dams
are currently planned in the Amazon basin alone
(65), and global road-building is likely to add
25 million km of paved roads by mid-century, almost all in developing countries (37). It is crucial
that planning of these developments analyzes
ecological effects as well as economic costs and
benefits, to decide where infrastructure should
be located to produce the most benefit for the
least cost. For example, an analysis of roads currently planned for the 2.3 million km2 Greater
Mekong region of southeast Asia mapped areas
where proposed developments are likely to furnish high gains in regional food production for
low environmental impact, mainly by catalyzing
higher productivity and market access in areas
already converted for farming, and other new
roads that would cause high impact for low gains
in total yield (66).
The challenges identified above, of using spatial
planning to optimize development versus conser-
vation and adequately financing conservation, are
being addressed in China through that country’s
ambitious Ecological Civilization plan (67). This
includes prioritization of nationwide land use and
infrastructure development based on a national
zoning of ecosystem function (Fig. 3C) that is
used to designate some areas as protected with
restricted development and others with differ-
ing levels of development intensity. The strategy
is being mainstreamed at all decision levels and
implemented through mechanisms that include
ecocompensation (of about 20 billion $US per
year) to areas where development is restricted
and other tools including Green GDP (gross do-
mestic product) auditing, carbon trading, pollution-
rights trading, and property rights.
Although conservation efforts have produced some
encouraging results, these have done little more
than forestall some losses by tackling symptoms
of unsustainable use of environments. Our successes have been valuable in buying time that could
allow recovery of species and ecosystems in the
future and providing lessons on how conservation actions can be made effective. However,
the problem of transforming the fundamental
drivers of unsustainable use of nature remains
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274 21 APRIL 2017 • VOL 356 ISSUE 6335 sciencemag.org SCIENCE
“All species are connected to
others through ecological
through ecosystems, as
do extirpations of local
populations and declines
in abundance, which are
widespread even in species
not close to extinction.”