From the late Pleistocene to the Holocene and now the so-called
Anthropocene, humans have been driving an ongoing series of species declines and
extinctions (Dirzo et al. 2014).
Large-bodied mammals are typically at a higher risk of extinction than smaller ones
(Cardillo et al. 2005). However, in some
circumstances, terrestrial megafauna populations have been able to recover some of
their lost numbers because of strong conservation and political commitment, as well
as human cultural changes (Chapron et al. 2014). Indeed, many would be in considerably
worse predicaments in the
absence of conservation action (Hoffmann et al. 2015). Nevertheless, most mammalian
megafauna face dramatic range
contractions and population declines. In fact, 59% of the world's largest carnivores
(more than or equal to 15 kilograms, n = 27) and 60% of the world's
largest herbivores (more than or equal to 100 kilograms, n = 74)
are classified as threatened with extinction on the International Union for the
Conservation of Nature (IUCN) Red List (supplemental tables S1 and S2). This
situation is particularly dire in sub-Saharan Africa and Southeast Asia, home to the
greatest diversity of extant megafauna (figure 1). Species at risk of extinction include
some of the world's most
iconic animals—such as gorillas, rhinos, and big cats (figure 2 top row)—and, unfortunately,
they are vanishing just as
science is discovering their essential ecological roles (Estes et al. 2011). Here,
our objectives are to raise
awareness of how these megafauna are imperiled (species in tables S1 and S2) and to
stimulate broad interest in developing specific recommendations and concerted action
to conserve them.
Figure 1.
A richness map of (a) the number of megafaunal species, (b) the number of
declining megafauna species, and (c) the number of threatened megafaunal
species in their native ranges. Megafauna are defined as terrestrial large
carnivores (more than 15 kilograms) and large herbivores (more than 100
kilograms). Threatened includes all species categorized as Vulnerable,
Endangered, or Critically Endangered on the IUCN Red List (see supplemental
tables).
Figure 2.
Photographic examples of threatened megafauna. Top row left to right: photos
of well-known species, including the Western gorilla (Gorilla gorilla) (CR),
black rhino (Diceros bicornis) (CR), and Bengal tiger, (Panthera tigris
tigris) (EN). Bottom row left to right: photos of lesser-known species,
including the African wild ass (Equus africanus) (CR), Visayan warty pig
(Sus cebifrons) (CR), and banteng (Bos javanicus) (EN). Photo credits: Julio
Yeste, Four Oaks, Dave M. Hunt, Mikhail Blajenov, KMW Photography, and
Kajornyot.
Megafauna provide a range of distinct ecosystem services through top-down biotic and
knock-on abiotic processes (Estes et al. 2011). Many megafauna function as keystone
species and ecological
engineers, generating strong cascading effects in the ecosystems in which they
occur. These species also provide important economic and social services. For
example, ecotourism is the fastest growing subsector of tourism in developing
countries (UNEP 2013), and megafauna are a
major draw for these tourists. Besides contributing considerable revenue to
conservation, wildlife-based tourism can contribute significantly to education,
economies, job creation, and human livelihoods.
Many of the surviving mammalian megafauna remain beset by long-standing and generally
escalating threats of habitat loss, persecution, and exploitation (Ripple et al.
2014, 2015). Large mammals are extremely vulnerable to these threats because
of their large area requirements, low densities (particularly for carnivores), and
relatively “slow” life-history traits (Wallach et al. 2015). Various anthropogenic
forces such as deforestation,
agricultural expansion, increasing livestock numbers, and other forms of human
encroachment have severely degraded critical habitat for megafauna by increased
fragmentation or reduced resource availability. Although some species show
resilience by adapting to new scenarios under certain conditions (Chapron et al.
2014), livestock production, human
population growth, and cumulative land-use impacts can trigger new conflicts or
exacerbate existing ones, leading to additional declines. According to the Food and
Agriculture Organization, as of 2014, there were an estimated 3.9 billion ruminant
livestock on Earth compared with approximately 8.5 million individuals of 51 of the
74 species of wild megaherbivores for which population estimates are available
within their native ranges (table S2), a magnitude difference of approximately 400
times.
The current depletion of megafauna is also due to overhunting and persecution:
shooting, snaring, and poisoning by humans ranging from individuals to governments,
as well as by organized criminals and terrorists (Darimont et al. 2015). Megafauna
are killed for meat and body
parts for traditional medicine and ornaments or because of actual or perceived
threats to humans, their crops, or livestock. Meat and body parts are sold locally,
sold to urban markets, or traded regionally and internationally. Striking instances
include the slaughter of thousands of megafauna, such as African elephants
(Loxodonta africana) for their ivory, rhinoceroses for their
horns, and tigers (Panthera tigris) for their body parts. In
addition, many lesser-known megafauna species (figure 2, bottom row) are now imperiled
(tables S1 and S2). Most of
the world's megaherbivores remain poorly studied, and this knowledge gap makes
conserving them even more difficult (Ripple et al. 2015).
Under a business-as-usual scenario, conservation scientists will soon be busy writing
obituaries for species and subspecies of megafauna as they vanish from the planet.
In fact, this process is already underway: eulogies have been written for Africa's
western black rhinoceros (Diceros bicornis longipes) and the
Vietnamese subspecies of the Javan rhinoceros (Rhinoceros sondaicus
annamiticus, IUCN 2015).
Epitaphs will probably soon be needed for the kouprey (Bos
sauveli), last seen in 1988; and the northern white rhinoceros
(Ceratotherium simum cottoni), which now numbers three
individuals (IUCN 2015). The Sumatran rhino
(Dicerorhinus sumatrensis) is already extinct in the wild in
Malaysia and is very close to extinction in Indonesia, with the population
collapsing during the last 30 years from over 800 to fewer than 100 (table S2). The
Javan rhino (Rhinoceros sondaicus) is down to a single population
of approximately 58 in a single reserve (table S2). The Critically Endangered
Bactrian camel (Camelus ferus) and African wild ass (Equus
africanus) are not far behind. Even in protected areas, megafauna are
increasingly under assault. For example, in West and Central Africa, several large
carnivores (including lions, Panthera leo; African wild dogs,
Lycaon pictus; and cheetahs, Acinonyx jubatus)
have experienced recent severe range contractions and have declined markedly in many
protected areas (IUCN 2015).
Although many of the general causes and mechanisms of declines are well identified
and recognized, this understanding has not translated into adequate conservation
action. Some of the existing mammal-prioritization schemes could be incorporated
into a comprehensive global strategy for conserving the largest mammals (Rondinini
et al. 2011). Increasing prioritization and
political will to conserve megafauna—and actions to restore or reintroduce them in
areas where they have declined or been extirpated (such as plans to reintroduce
scimitar-horned oryx into Chad and to rehabilitate the entire Gorongosa ecosystem
in
Mozambique)—are urgently needed. We suggest that the problem has two parts: (1) a
need to further and more effectively implement, expand, and refine current
interventions at relevant scales and (2) a need for large-scale policy shifts and
global increases in funding for conservation to alter the framework and ways in
which people interact with wildlife.
In order to save declining species, there is a need to increase global conservation
funding by at least an order of magnitude (McCarthy et al. 2012). Without such a transformation,
there is a risk that
many of the world's most iconic species may not survive to the twenty-second
century. We must not go quietly into this impoverished future. Rather, we believe
it
is our collective responsibility as scientists who study megafauna to act to prevent
their decline. We therefore present a call to the broader international community
to
join together in conserving the remaining terrestrial megafauna (see declaration in
box 1).
Box 1.
A declaration to save the world's terrestrial megafauna.
We conservation scientists
Acknowledge that most of the terrestrial
megafauna species are threatened with extinction and have declining
populations. Some megafauna species that are not globally threatened
nonetheless face local extinctions or have Critically Endangered
subspecies.
Appreciate that “business as usual” will
result in the loss of many of the Earth's most iconic species.
Understand that megafauna have ecological
roles that directly and indirectly affect ecosystem processes and
other species throughout the food web; failure to reverse megafaunal
declines will disrupt species interactions, with negative
consequences for ecosystem function; biological diversity; and the
ecological, economic, and social services that these species
provide.
Realize that megafauna are epitomized as a
symbol of the wilderness, exemplifying the public's engagement in
nature, and that this is a driving force behind efforts to maintain
the ecosystem services they can provide.
Recognize the importance of integrating and
better aligning human development and biodiversity conservation
needs through the engagement and support of local communities in
developing countries.
Propose that funding agencies and scientists
increase conservation research efforts in developing countries,
where most threatened megafauna occur. Specifically, there is a need
to increase the amount of research directed at finding solutions for
the conservation of megafauna, especially for lesser-known
species.
Request the help of individuals, governments,
corporations, and nongovernmental organizations to stop practices
that are harmful to these species and to actively engage in helping
to reverse declines in megafauna.
Strive for increased awareness among the
global public of the current megafauna crisis using traditional
media as well as social media and other networking approaches.
Seek a new and comprehensive global commitment
and framework for conserving megafauna. The international community
should take necessary action to prevent mass extinction of the
world's megafauna and other species.
Urge the development of new funding mechanisms
to transfer the current benefits accrued through the existence
values of megafauna into tangible payments to support research,
conservation actions, and local people who bear the cost of living
with wildlife in the places where highly valued megafauna must be
preserved.
Advocate for interdisciplinary scientific
interchange between nations to improve the social and ecological
understanding of the drivers of the decline of megafauna and to
increase the capacity for megafauna science and conservation.
Recommend the reintroduction and
rehabilitation, following accepted IUCN guidelines, of degraded
megafauna populations whenever possible, the ecological and economic
importance of which is evidenced by a growing number of success
stories, from Yellowstone's wolves (Canis lupus)
and the Père David's deer (Elaphurus davidianus) in
China to the various megafauna species of Gorongosa National Park in
Mozambique.
Affirm an abiding moral obligation to protect
the Earth's megafauna.
From declaration to action
Social and political commitment to provide sufficient protection across the vast
landscapes needed for the conservation of the world's megafauna is increasingly
required. International frameworks and conventions such as the Convention on
Biological Diversity (CBD), the Convention on the Conservation of Migratory Species
of Wild Animals (CMS), and the Convention on International Trade in Endangered
Species of Wild Fauna and Flora (CITES) have had some success in safeguarding
species. However, the decisions of these conventions are not always binding, and
they will require substantially increased political will and financial support if
they are to be effective in the critical task of securing the survival of the
world's megafauna. Some regional instruments such as the CMS Gorilla Agreement and
the Global Tiger Initiative incorporate environmental or biodiversity commitments
and are playing a growing role in protecting biodiversity. International agreements
are often well placed for enforcing regional frameworks for megafauna; examples
include the African Elephant Action Plan and the regional conservation strategy for
cheetahs and African wild dogs. However, the implementation of such initiatives
requires financial resources and capacity that are seldom available at those
locations where the highest diversity of megafauna remains (figure 1). Therefore,
the onus is on developed
countries, which have long ago lost most of their megafauna, to not only embark on
conservation and restoration programs on their own lands but also support
conservation initiatives in those nations where diverse megafauna still persist. For
conservation efforts to be successful, actions should be taken at all levels by
authorities who have the public interest in mind and who work to secure the
continued existence of these species.
Successfully conserving megafauna requires bold social, political, and financial
commitments from nations around the world. Through understanding the value and
importance of local human needs and by combining international financial support
with a coordinated multilateral approach to conservation, it may be possible to
rescue megafauna from the brink of extinction. As biologists, ecologists, and
conservation scientists, we are mindful that none of our arguments are new and that
our prescriptions are far easier to write out than to accomplish. However, our
objective in presenting them together here is to demonstrate a consensus of opinion
amongst the global community of scientists who study and conserve these animals,
thereby emphasizing to the wider world the gravity of the problem. Our hope is that
this declaration, with the proposed actions and list of signatories, will attract
the public and media attention that this issue requires to galvanize opinion,
catalyze action, and establish new funding mechanisms. Comprehensive actions to save
these iconic wildlife species will help to curb an extinction process that appears
to have begun with our ancestors in the late Pleistocene.
In the supplemental material for this article, this entire paper is available in six
other languages: Spanish, Chinese, French, Portuguese, Malay (Bahasa Malaysia), and
Thai.
Supplementary Material
Supplementary Data
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