The sharp decline in numbers of the world’s largest herbivores could leave Africa and Asia with “empty landscapes” if the trend is not reversed, scientists have warned.

Populations of large herbivores such as elephants, zebras, buffalo, giraffes, hippos, rhino and tapirs are currently declining at a rate that is considered unsustainable.

A study, published in the journal, Science Advances, that focused on 74 large herbivore species — animals that depend on vegetation — concludes that, without a far-reaching global intervention, the animals will continue disappearing from many regions in Africa and Asia, with enormous ecological and socio-economic costs.

“The rate of large herbivore decline suggests that swathes of the world will soon lack many of the vital ecological services these animals provide, resulting in enormous ecological and social costs,” the scientists warned in their report.

The study was conducted by a team of renowned international wildlife ecologists who undertook a comprehensive analysis of data on the world’s largest herbivores, weighing more than 100 kilogrammes, focusing mainly on their endangered status, main threats and ecological consequences of population decline.

Though the researchers did not name the species, they stated that four large herbivores are under threat in Kenya, Uganda, Rwanda and Burundi, while three are in danger in Tanzania. In Somalia and Ethiopia, five face extreme threats.

But other studies have mentioned elephants, rhinos, zebras, eland and giraffes as some of the herbivores under threat.

East Africa has a very high variety of large herbivores, making it one of the most important biodiversity regions in the world. Kenya and Tanzania, for example, have as many as 19 species of large herbivores, compared with countries in North Africa and Europe, which have only one.

READ: Africa is fast losing its wildlife as population pressure mounts

Concerted effort

The extinction of some carnivores and herbivores would negatively impact the African continent, given the fact that wildlife is a major tourist attraction and has been a source of foreign exchange for many countries. Any decline in the number and variety of wild animals will negatively affect the tourism sector, which thousands of individuals depend on for their livelihood.

“This is why East African countries should take the conservation of large herbivores seriously since we will be among the heaviest losers not only in terms of tourism but also in biodiversity,” said conservationist James Kiyangah, who works with communities in Kenya to promote ecotourism.

Nearly all the threatened species are in developing countries where major threats likes hunting, land-use change, and resource depression by livestock are taking their toll of unique ecosystems, mainly desert lands, savannah grasslands and natural forests.

“Loss of large herbivores can have cascading effects on other species including large carnivores, scavengers, mesoherbivores, small mammals, and ecological processes involving vegetation, hydrology, nutrient cycling, and fire regimes,” the scientists added.

The study found a link between the reduction in the numbers of large carnivores and the decline in the population of herbivores in Africa and Asia.

Lions are one of the large carnivores whose decline in sub-Saharan Africa has been worrying scientists. An earlier study conducted by scientists from Duke University in 2012 found that the lion population in Africa has decreased by almost two-thirds over the past 50 years, predicting that as few as 32,000 lions may be left on the continent.

According to the latest study, 44 of the 74 largest terrestrial herbivores — almost 60 per cent — are listed as threatened with extinction (including 12 critically endangered or extinct in the wild), and 43, — approximately 58 per cent — have decreasing populations.

Most large herbivores are found in Africa (32), Southeast Asia (19), India (14), China (14) and the rest of Asia (19). Fewer species are found in Europe (7), Latin America (5) and North America (5).

READ: Northern white rhinos face extinction with only five left on earth

Overall 71 species occur in developing countries, whereas only 10 occur in developed countries. “The highest number of threatened large herbivores occurs in Southeast Asia (19, east of India and south of China), followed by Africa (12), India (9), China (8), Latin America (4), and Europe (1),” the study added.

The scientists found the main threats to large herbivores, both in Africa and Asia, are hunting, competition with livestock, and land-use change such as habitat loss, human encroachment, cultivation, and deforestation.

“Hunting for meat across much of the developing world is likely the most important factor in the decline of the largest terrestrial herbivores,” the study said.

Mr Kiyangah said illegal trade in bush meat is still thriving in the region and is common in areas surrounding protected lands.

Since wildlife populations outside of protected areas are declining, the wildlife ecologists warned that hunters are shifting their attention to populations in national parks and game reserves, with some success given the fact that protected area management budgets for guarding wildlife from poaching are often inadequate on the two continents.

To prove their claim, the scientists said between 1970 and 2005, large mammal populations in Africa’s protected areas decreased by about 59 per cent, adding that the decline will continue if concrete action is not taken.

In addition, the study published in the journal Science Advances says slow reproduction makes large herbivores particularly vulnerable to overhunting, and the largest- and slowest-to-reproduce species typically vanish first, “and as they disappear, hunters turn to smaller and more fecund species, a cascading process that has likely been repeated for thousands of years.”

In fact, hunting for meat has increased in recent years due to human population growth, in both Africa and Asia, resulting in greater access to virgin lands through construction of roads, use of modern firearms and wire snares.

The latest study said saving the remaining threatened large herbivores will require concerted action from both rich and poor countries. The world’s wealthier populations, for example, will need to provide the resources essential for ensuring the preservation of the global natural heritage of large herbivores.

“A sense of justice and development is essential to ensure that local populations can benefit fairly from large herbivore protection and thereby have a vested interest in it,” the scientists said.

Lowering human consumption of domestic ruminants could help conserve herbivore populations by reducing demand for rangeland forage, water, and feed crops.

In addition, reducing consumption of wild herbivores can also be effective, and enforced wildlife management such as through wildlife ranching has proven to be very successful at maintaining sustainably high harvests of wild meat while providing subsistence food resources to local people.