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Hunting and poaching animals is one of the leading drivers of biodiversity loss. For mammals, birds, and some other species groups, it is the biggest threat. This risk is compounded by growing markets for wildlife trade: luxury foods, pets and medicinal remedies is itself a dominant risk. In fact, some of the world’s most charismatic species have already gone extinct as a result of wildlife trade. As we saw in our work on elephant populations, the last Javan rhino, Rhinoceros sondaicus annamiticus in Vietnam was shot for its horn in 2010. This subspecies is now extinct. The Northern White rhino is also on the brink of extinction – there are only two individuals left, and both of them are female.

It’s a complex problem. Many communities – particularly in poorer countries – rely on bushmeat for subsistence, or income from traded animals and body parts to feed their families. This is nothing new. Humans have hunted wild mammals and other wildlife for millennia; our ancestors drove hundreds of the world’s largest mammals to extinction as they migrated out of Africa. But the problem has been heightened by population growth, increased connectivity to markets, commercialization of luxury goods, and better technologies to catch and sell wildlife parts.

The route out of this problem is also not straightforward. Richer countries managed to switch from wild catch to livestock of their own. Lots of cattle, pigs and chickens (as we explore here). This probably saved a lot of wild animal populations from total demise. But the expansion of agricultural land for livestock has also come at a high environmental cost. Deforestation and habitat loss is a close second to poaching as the leading driver of biodiversity loss. We see this in many middle-income countries today: more than 40% of the world’s deforestation is driven by the expansion of pastures for beef. By transitioning from wild game to livestock, countries will save precious species from extinction by hunting, but put increasing pressures on wildlife through habitat loss. Without solutions such as alternative proteins, lab-grown meat, or a massive shift in attitudes towards plant-based sources of protein, it’s hard to see a way out of this that avoids large ecological damage.

But it’s not just our concern for other species that should motivate us to take wild hunting and poaching seriously. There’s also a more selfish reason: zoonotic diseases, and the risk of future pandemics. Given the tragic consequences of the Coronavirus (COVID-19) pandemic, the need to take this risk seriously should be obvious. There are several reasons why the overexploitation of wildlife – and large mammals in particular – can increase the likelihood of zoonotic disease outbreaks. Firstly, the basic nature of hunting, gathering and preparing wild meat increases the risk of transmission to humans: there can be high levels of direct contact of body fluids, which is thought to have been an important factor in the emergence of diseases including Ebola, HIV, Anthrax, Salmonellosis, and many others. Second, the selective loss of large mammals and primates (we tend to hunt larger animals in particular) changes the dynamic of ecosystems; when larger animals disappear, populations of smaller animals including rodents tend to flourish. Rodents are very effective hosts and spreaders of diseases that can transfer to humans. Even if you don’t care about other species, there’s a strong human case for better management and regulation of hunting and wildlife trade.

In this article we will look at the impacts on animal populations; the scale of global wildlife trade; what we trade wildlife for; how this is changing; and what determines the intensity of human poaching. Exploring these questions should give us an insight into the drivers of these practices, and help us understand what we can do to tackle it.

What impact has hunting and wildlife trade had on animal populations?

The historical impacts of human hunting on mammal populations has been well-documented. You only need to follow the timing of mammal extinction events to trace the footsteps of human arrival across the world’s continents. When we arrived, large mammals soon disappeared. The dramatic decline of whale populations over the 20th century as a result of hunting is another stark example: the Blue Whale was almost plunged into extinction, losing 99% of its numbers.

Let’s look at the recent and current threats that modern exploitation poses to the world’s mammals and birds. Overhunting is the leading threat to biodiversity. Across the tropics, an increasing number of areas can be described as “half-empty” or “empty” ecosystems – and the strongest predictor of these areas is not forest area, habitat type, or protection status. It’s the local patterns of hunting. 

Many studies have documented large declines in wildlife populations due to overhunting. In a meta-analysis, published in the journal Science, Ana Benítez-López and colleagues assessed the impact of hunting on tropical bird and mammal populations.1 The meta-analysis included 176 studies, covering 97 bird and 254 mammal species. It found a 58% decline in bird, and 83% decline in mammal abundance in hunted versus unhunted areas. Another meta-analysis, published in Nature, focused on the impact of wildlife trade on mammal, bird and reptile populations. Oscar Morton and colleagues found a 62% decline in species abundance where wildlife trade was present. Exploitation for bushmeat trade drove a 60% decline in populations.2

This decline in animal populations is pushing some species towards extinction. As I mentioned earlier, the Javan rhino was poached to extinction by its lucrative horn. Many others are facing the same fate. One-quarter of the world’s mammal species are threatened with extinction. In a study published in the Royal Society, William Ripple and colleagues estimated that bushmeat hunting was the primary threat for one-quarter (26%) of those at risk.3 That’s 301 terrestrial mammal species. All of them are in the tropics.

How much wildlife is traded across the world?

Animals can be hunted as subsistence for meat. But there is a much bigger, and growing, market for wild meat and other animal products. These markets exist locally, nationally, but also internationally as traded goods between countries. The global industry for wildlife trade – which includes regulated and unregulated, legal and illegal trade – is estimated to be worth between US$4-20 billion per year.4

How many species are traded across the world?

In a study published in Science, Brett Scheffers and colleagues assessed the scale of global wildlife trade. They found that one-quarter (24%) of vertebrate species are traded globally. That’s 7638 species. In the chart we see how this breaks down by taxonomic group. Birds are the most-traded group, with 45% of species being traded. 23% of mammals; 13% of reptiles; and 8% of amphibians were also traded.

What does this amount to in total numbers of animals or organisms that are traded? For obvious reasons, putting a definitive number on animals that are traded – both legally and illegally – is hard. Unsurprisingly, sellers are not forthcoming in reporting illegal trade. However, legal trade is tracked by the CITIES Trade database, run by the UN Environment Programme.5 The charts here show how the reported trade of organisms – plants and animals – has changed since the 1970s.6 This is shown as the total size of wildlife exports but also as the breakdown by taxonomic group: mammals, reptiles, birds etc.

Obviously wildlife is traded in different ways: sometimes as live, whole organisms and sometimes as specific body parts (such as skins, horns, or tusks). To provide a more consistent way of monitoring trade, the authors measure it in ‘whole organism equivalents (WOE)’. For example, five skulls represent five WOEs, whereas it’s assumed that four ears are sourced from two animals and so represent two WOEs.

Wildlife is legally traded in large volumes. The average over the decade from 2005 to 2014 was over 100 million WOEs per year. This is a more than ten-fold rise on the decade from 1975 to 1985.

Plants are, by far, the most traded group. 1.8 billion exports have been reported since 1975. This was followed by reptiles (152 million) invertebrates (80 million); birds (24 million); mammals (13 million); fish (13 million) and amphibians (1 million).

What is wildlife hunted and traded for?

The scale of hunting and wildlife trade is large. But there are many reasons that animals are traded, and not all of these industries will put species at equal risk of population declines or extinction. Some are traded as pets. Some as products. Some are traded as live organisms, some for specific body parts.

Let’s first look at mammals, and why they’re hunted and traded. Earlier we saw that hunting was the biggest pressure for 301 threatened mammal species. What are they used for? Meat for human consumption was the most common: 285 species were used for meat consumption, primarily across lower income countries. But it’s not just about subsistence food supply: hunters also make a living from selling them. 67 species were used for traditional medicines; 46 as live animals for the pet trade; and 36 for the ornamental use of body parts. These ornamental uses include parts such as ivory, horns, antlers and skins. In the chart we see the scale of rhino poaching across the world.

This maps closely on to the composition of traded wildlife beyond mammals. In the chart we see how frequently different taxonomy groups are traded as pets, and as products. Some species are traded as pets and products (which is why the percentage for each doesn’t sum to 100%). But there are clear differences in preferences across the groups. Birds and reptiles are much more likely to be traded as pets, either as household pets or for industries like zoological gardens or circuses. 85% of traded bird species are traded as pets. Mammals are much more likely to be traded as products: elephant trunks, rhino horns, deer antlers, and gorilla hands are all common trophy products that are driving some beautiful animals to extinction.

Why are some animals hunted more than others? Can we predict where hunting might occur?

If we want to protect the world’s animals from overexploitation we need to know which ones are most susceptible to hunting, and where and when this might be most intense.

Most poaching today occurs in the tropics. Particularly in lower-income countries where communities rely on hunting for food, and market products to sell. Within these countries there are a couple of useful predictors of hunting intensity.

Animal size and uniqueness

Can we predict what types of animals might be at greatest risk from hunting?

Larger mammals have always been at the greatest risk from humans. We see these effects date as far back as humans’ migration out of Africa across the world’s continents.

This still applies today. In total numbers, hunting affects the most species which weigh less than 10 kilograms. But as a percentage of the total number of species in each size category, it’s the largest ones that are most at risk. Almost 60% of large terrestrial mammals (which weigh more than one tonne) are at risk of extinction through hunting.

But it’s not just about size. How distinctive an animal is also matters. Having unique traits or features makes an animal particularly attractive in wildlife markets: they’re earmarked for traditional medicines, or are lucrative collectors’ items for trophy hunters. A species’ evolutionary distinctiveness (measuring how isolated they are in the ‘tree of life’) is a strong predictor of being traded in wildlife markets. That’s why animals like elephants, rhinos and pangolins are under such pressure.

Distance to markets

Historically, humans would hunt animals to feed themselves and their tribes. It was very much a subsistence way of living. Things are very different today with increased connectivity between villages, towns, cities and places of wilderness. Roads now pass through previously pristine landscapes. These provide perfect access points for poachers to deliver their hunt to local markets.

Indeed, the research finds that one of the strongest predictors of hunting pressure and trade-induced declines in animal populations is the proximity to markets. Animal populations saw the greatest decline in areas where the travel time to human settlements (with more than 5,000 people – large enough for markets to form) was the shortest. As the distance from local or national markets increased, the impact on animal populations decreased. This was true at both local and national-level scales. 

As countries improve the connectivity between villages and towns, the line between dense human settlements and wilderness becomes more and more blurry.

Market prices and levels of poverty

People hunt and sell animals and their body parts as a source of income. We might therefore expect poaching rates to be associated with the prices that goods can sell for, and levels of poverty in local populations. Poorer communities may be more reliant on these sales as a source of income. The research suggests that market prices are strongly associated with poaching intensity: one study found strong correlation between ivory price and annual variation in poaching rates. Site-level variations in poaching rates were also related to poverty rates, with higher rates in communities with more people living in extreme poverty.

Protected areas

An obvious solution to poaching would be to increase the number and extent of protected areas. This, of course, rests on the assumption that protected areas are successful in preventing it. Is this really true?

The research suggests that protected areas reduce, but do not eliminate hunting. Animal populations within many protected areas are still shrinking, but slower than populations outside these areas. Wildlife trade still drove average declines of 56% in mammal populations in protected areas, compared to 71% in unprotected areas. This is still worrying.

A lot of protected areas across the Amazon, Africa and Asia have very little safeguarding and on-ground monitoring efforts. Simply designating an area as protected is not enough to safeguard wildlife. It needs proper reserve management, law enforcement and local monitoring on-the-ground. Protected areas that did have guards enforcing hunting and trade bands had significantly lower rates of decline: 39% versus 65% in areas without this local protection.

Increasing the scope of protected areas is therefore important. But to be successful, we will need much more stringent enforcement at local levels.

Explore more of our work on Biodiversity