Dramatic decline in scavengers in southern Africa could affect spread of disease
This is why the decline of Africa’s threatened vultures is uniquely problematic for socio-ecological systems, says a new paper, A Conservation Criminology-Based Desk Assessment of Vulture Poisoning in the Great Limpopo Transfrontier Conservation Area, published in the journal Global Ecology and Conservation.
“Conservation stakeholders have identified evidence that a number of vulture species in particular ecosystems are being systematically targeted by poisoning with potentially significant effects on human, wildlife and ecosystem health,” says the paper.
It describes how in socio-ecological systems already experiencing harms associated with the illegal wildlife trade and human-wildlife conflicts, the collateral impacts from vulture poisoning on humans and animals “may be overwhelming at best and irreversible at worst”.
“The literature is providing new evidence that unlike declines of other species like rhino, declines in apex scavengers such as vultures are likely to drastically alter food webs... with implications for carrion removal and disease-regulation services.
“Preventing poison-related harm to vultures is more efficient and effective than responding to such events because the impacts of poisoning are often fatal for the birds and other affected wildlife and not always detectable, and potentially unresolvable for humans.”
The authors are from Michigan State University, the University of Cape Town, University of Maryland, University of Houston, University of KwaZulu-Natal, the Endangered Wildlife Trust, Ezemvelo KwaZulu-Natal Wildlife, BirdLife International and BirdLife SA.
Many African countries have legislation that specifically addresses the use of poison for killing wildlife, yet “chemicals remain readily available and are known to be traded through licit and illicit channels in both large and small quantities," state the researchers.
“The impacts of these chemicals can cascade across ecosystems as they indiscriminately poison non-target carnivores, insects and scavengers, including vultures,” and present significant human and environmental threats, too.
From April 2009 to April last year, there were 99 reported wildlife poisoning incidents, with 6932 vultures killed, and/or harmed, in Botswana, Mozambique, Namibia, South Africa, Tanzania, Zambia and Zimbabwe, according to the paper.
Last June, elephant poachers poisoned 537 vultures in northern Botswana, the largest mass-poisoning of vultures in southern Africa.
In 2013, in Namibia, 500 vultures were killed after feeding on a single poisoned elephant carcass.
Vultures are among the most threatened groups of birds worldwide, with 69% of all vulture species listed as threatened, or near-threatened, with most of these classified as endangered or critically endangered.
Worldwide, vulture declines are being driven by poisoning, electrocutions on and collisions with energy infrastructure, harvesting for illegal trade and bushmeat, and land-use changes, among other human-related activities.
“Africa’s vulture populations are emblematic of worldwide loss in biodiversity in that in just three generations, seven species have declined by at least 80%, four species have been uplisted to critically endangered, and two species to endangered.”
Of the known vulture poisoning incidents across southern Africa, at least 15% occurred in the Great Limpopo Transfrontier Conservation Area (GLTFCA), “an area of broad concern for wildlife-poisoning events”. Among the total number of birds poisoned in the Gonarezhou, Kruger and Limpopo national parks between 2008 and 2019, vultures comprised 99%, 78% and 90%, respectively.
Lion poaching for belief-based use in the GLTFCA has added a “new aggravation” for local vulture conservation since 2014, as poison was the most common means of killing lions.
The dramatic increase in the poaching of elephants for ivory in southern Africa, in particular, to supply the global illegal wildlife trade, has been linked to huge increases in mass-poisoning events of vultures.
Vultures “circle” in the skies above a carcass when scavenging, serving as one of many sentinels for law enforcement authorities, “who can use vultures as a cue to help them locate illegal poaching activities and potentially enhance their ability to apprehend poachers and/or forensic science”.
Between 2012 and 2014, 11”sentinel” poaching incidents were recorded across seven, predominantly southern African countries, where 155 elephants were killed and de-tusked - and 2044 vultures poisoned, says the paper, noting how a significant number of vultures can be killed at a single elephant carcass.
“Vulture mortalities from poisoning events associated with elephant poaching for ivory have increased more rapidly than with other types of poisoning, accounting for one third of all vulture poisonings recorded in African since 1970.”
Sentinel poisoning has particularly acute and negative impacts on local vulture populations, and unchecked, will “likely cause spatially explicit local extinction of white-backed vultures in the Kruger National Park in less than 60 years”.
Human-wildlife conflict also drives vulture killings.
“Livestock owners may illegally lace fruit, meat, animal carcasses and waterholes with poison such as highly toxic pesticides to kill animals such as lion, cheetahs, or black-backed jackal in retaliation or to prevent depredation.”
Belief-based use contributes to almost 30% of vulture deaths across the continent.
“Many species of birds and their body parts are harvested for market trade; the birds are often killed directly with poisons or collected as a by-product of poisoning events...
"It has been reported there are an estimated 59000 vulture-part consumption events in South Africa each year, involving an estimated 1250 hunters, traders and healers," reveals the paper.
“As with human-wildlife conflict, the indiscriminate risks from chemicals used to kill vultures for belief-based use have substantial health implications because traders, healers and end users of vulture parts may come into contact with poisons.”
Ripple effects pose increased risks
The team of researchers do not explicitly advocate for the criminalisation of those involved in vulture poisoning, nor necessarily for increased law enforcement activities, “as this may be detrimental to rural populations who are dependent on bushmeat.
“However, the ripple effects present in the socio-ecological system within which vultures reside pose increased risks to human populations due to the potential proliferation of disease and other outcomes resulting from the removal of these efficient scavengers.
“Regulations exist to control risks associated with poison, yet violations of the law persist. Such non-compliance undermines conservation activities, designed to conserve vultures and other wildlife species, and support for sustainable rural livelihoods such as avitourism or building wildlife economies.”
Strategies to prevent vulture poisoning in the GLTFCA include banning chemical sales in small quantities in human population areas close to park boundaries or transnational borders; leveraging local communities as guardians in communal conservancies and effective compensation and benefit sharing from the wildlife economy in farm and ranching communities.