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Can We Live without Large Herbivores?

In May, 134,000 saiga antelope died in central Kazakhstan. Credit:serg2015/adobe

In May, 134,000 saiga antelope died in central Kazakhstan. Credit: serg2015/adobe

By Thomas Newsome & William Ripple

The collapse of large herbivore populations around the world has dire ecological and social consequences.

In May this year, 134,000 saiga antelope died in the space of 2 weeks in central Kazakhstan. That was about half the world’s population of this endangered antelope species.

The exact causes of the mass antelope die-off are still unknown, but this alarming event raises the question of whether we can live in a world without large herbivores.

Some 100,000 years ago, during the Pleistocene, we started to lose a suite of herbivores, particularly mega-herbivores larger than 1000 kg. Changes in climate are often invoked as the cause, but overhunting by humans was likely a contributing factor.

During the Pleistocene in Australia, for example, there were iconic species such as Diprotodon, which was the size of a rhinoceros. There were also giant kangaroos that stood up to 3 metres tall. Preying upon these animals was another giant, the marsupial lion. All are now extinct.

The extinction of these creatures can be viewed as a natural experiment that highlights the scale of ecological impacts arising from the loss of large herbivores. The loss of those giant grazers in Australia, in combination with increased fire in the landscape, triggered the replacement of mixed rainforests by sclerophyll forests, which included species more tolerant of drought and fire.

In other areas, such as North America, the extinction of mega-herbivores gave rise to the formation of novel plant communities. And in Europe, the mosaic of vegetation structures was replaced with more closed woodland communities.

Today there are only 74 herbivore species left with a body mass greater than 100 kg. Sadly, 44 are listed as threatened with extinction, 12 are critically endangered or extinct in the wild, and 43 have decreasing populations according to IUCN criteria.

Human actions still pose the greatest threat to the survival of these 74 large herbivores. By far the biggest threat is exploitation by humans, including hunting for meat and body parts. Competition with livestock is another big threat, as well as land-use changes such as habitat loss, human encroachment, cultivation and deforestation.

Ecological Consequences

What is particularly concerning is that many of these large herbivores perform important ecological functions. If the threats continue, these functions will be lost forever, resulting in enormous ecological costs.

For example, elephants convert woodland to shrubland by trampling vegetation and damaging trees. This improves the browsing availability for other herbivores like impala and black rhinoceros.

When elephants damage trees they even provide better habitats for lizard communities. And, by opening up the vegetation they facilitate predators by allowing them to move through what would otherwise be impenetrable thicket.

Elephants, along with many other large herbivores, are also great dispersers of seeds over long distances, which helps to maintain the distribution and abundance of tree species.

Hippopotamus maintain pathways in swamps, and birds feed off the insects on their backs. The areas where hippopotamus graze are also more nutritious for other grazers.

Similarly, white rhinoceros maintain short grass patches, which increases food for species like impalas, wildebeest and zebras.

Even the dung of herbivores plays an important role in maintaining ecosystem health by returning nutrients back to the soil at a faster rate than leaf loss and decay. Dung piles essentially become concentrated nutrient patches, and some frog species use the dung piles as a home when leaf litter is scarce.

More broadly, herbivores are the primary source of food for predators like lions, tigers, leopards and wolves. Herbivore carcasses provide a source of food for scavengers. In Yellowstone National Park, for instance, grey wolves leave behind elk carcasses, which provide food for coyotes, foxes, ravens and eagles during winter when food is scarce.

The sad reality is that the loss of herbivores in the ecosystem will not only impact on other species, but it could inadvertently increase the intensity of wildfires because of increased fuel loads due to the decline of vegetation consumption by these species.

Rodent outbreaks could also become more common because of the increased availability of food. With that comes the threat of disease outbreaks, negative effects on some plant communities, and increases in predators that specialise on rodents.

The decline of large herbivores also has social costs for humans. Herbivores provide a primary source of food for more than a billion people who rely on wild meat for subsistence. Thus, under a business-as-usual scenario, food security will continue to falter given that wild meat is expected to decline by more than 80% during the next 50 years in some regions.

The herbivores that we are losing draw many tourists to protected areas, especially where they occur with large predators. Can you imagine visiting Africa and seeing no elephants or lions? Tourist numbers would plummet and thereby destroy an industry that supports employment in this developing region.

What Can Be Done?

Some solutions to avoid the imminent threat of large herbivore extinctions have been around for decades, such as increasing the size of protected areas, restoring degraded habitats, providing more wildlife corridors, mitigating climate change and reintroducing locally extinct species.

Ultimately though, we have an increasing human population, and per capita resource consumption levels are well beyond sustainable levels. This means that reduced human birth rates must become a priority for conservation, but it can only be achieved by providing educational and development opportunities in the developing world, especially for young women.

Human consumption of meat must also be addressed. In some areas of the world, like North America and Europe, the number of livestock being grazed has remained relatively stable over the past 50 years while in other areas like China, Asia and Africa, livestock numbers have been rising over the same period. Reducing the consumption of livestock must be part of the solution, because demand for water, crops and land will be reduced, in turn providing more space, food and water for wild herbivores.

But providing more space is only an effective solution if there are adequate protections in place to conserve the wild herbivores. This means that humans need to reduce their illegal consumption of wild herbivores as bush meat, and stop illegally poaching body parts like rhino horns.

To do so, bold new policies are urgently needed that increase the effectiveness of law enforcement, provide incentives for local communities to conserve wildlife, reduce demand for illegally sourced body parts, and aid a shift away from luxury wildlife products in countries such as China and Vietnam.

There is also a need for research of threatened species that are rarely studied. We know a lot about the herbivores that are not even threatened, like red deer, reindeer and moose, yet there are suites of threatened large herbivores in South-East Asia, Africa and Latin America in need of immediate attention.

Most people have probably never heard of them, but species that need attention include the critically endangered tamaraw, the Visayan warty pig and the walia ibex, as well as the endangered Oliver’s warty pig, mountain anoa, lowland anoa and mountain tapir. A special fund is needed to finance graduate students to conduct research on these species before they literally disappear without being noticed.

Unless we can make these changes, the wave of species extinctions that obliterated 80% of the Pleistocene mega-herbivores will continue. We will lose the important ecological services that herbivores provide, and we will be left with dramatically transformed landscapes across much of the planet.

Thomas Newsome is a postdoctoral research assistant of the School of Biological Sciences at The University of Sydney. He completed a postdoctoral fellowship funded by the Australian-American Fulbright Commission at Oregon State University, where William Ripple is a Distinguished Professor of Ecology in the Department of Forest Ecosystems and Society. This article is based on research published in Science Advances (http://tinyurl.com/lukadhv).