Wild animals reduce disease risk so we shouldn’t kill them

For obvious reasons, there is a lot of talk at the moment about the risk of getting diseases from animals. We degrade habitatsWhat is habitat for animals and people? Habitat, hence the word "habitable" describes the natural surroundings in which any animal (or human) lives, that houses basic needs, such as food and shelter. Vegetation, for example, is habitat for animals. On its own, habitat is not necessarily stable or sustainable, which is why it differs from an ecosystem. Habitat in disrepair More, illegally harvest wildlife and mix them with domestic animals in markets. This obviously increases our exposure to diseases like coronavirus or ebola. But wild animals reduce disease risk. As always we jump to killing animals as a solution for everything. As we discover, this makes things worse.

Killing more animals makes things worse

The problem for wildlife, is when authorities start issuing bounties, in an ill-informed effort to reduce the risk. Transmission of tuberculosis (TB) between wild animals and cattle caused the UK government to cull more than 100,000 wild badgers.

Being one of the UK’s remaining examples of mammal megafaunaThe largest animals that represent the top of the trophic pyramid. These are the final building blocks in ecosystem structures for maximum entropy production. Megafauna can be measured at any spatial scale. The largest animal that ever lived on Earth is the Blue Whale. In a grassland, spiders could be considered megafauna The term is generally reserved for animals larger More, this will have had untold impact on the ecosystem-integrity of an already fragile farming system that’s facing imminent wide-scale loss of soil fertility. Badgers no longer have any natural predators. Brown Bears and Wolves went extinct in the UK over 1,000 years ago and Golden Eagles [1], once widespread, are now only found in the far north of England and Scotland.

When it comes to disease, the risk of animal-to-human transfer(of nutrients) the thing that sets animals apart from plants, is that they can move. Some of the biggest migrations on Earth every day, are the movement of insects like caterpillars, from the stem of a plant to a leaf and back, before turning into butterflies and transferring the energy elsewhere. Large-scale migration of grazing animals and migratory songbirds moves More declines when ecosystemsHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More harbour natural predator-prey relationships. It’s quite obvious why. Being diseased makes animals more prone to predation. This means predators eat more diseased animals, leading to lower overall infection rate.

Restoring wildlife populations reduces disease risk

A study published in the journal Nature in 2019 [1] used a combination of field data and a theoretical model to look at the animal impactWhat is Animal Impact? Without wildlife, Earth would not be habitable for humans, because it's animals that stabilise ecosystems. It’s a fundamental law of nature that animals (and humans) exist because we are the most likely lifeforms to minimise environmental chaos. Animal impact, therefore, is a measure of how much all wildlife is collectively responsible for creating a habitable Earth. The More of wolves on the prevalence of TB in wild boar. On the whole, for scenarios studied, the presence of wolves had a massive effect on disease prevalence. They could almost wipe it out of the wild boar population altogether. Other studies find Lyme’s disease increased as small mammal predators were removed from the wild. This tick-borne disease is potentially fatal for humans.

The scientists modelled both a short-term and long-term scenario. In the short-term scenario (above, left), wolf numbers were allowed to increase. This stabilised wild boar populations. It reduced disease prevalence by 5x over 14 years and almost wiped out the disease by 2050. In the long-term scenario (above, right), researchers assumed wolves would be hunted from about 2015 and decline. This led to a rapid increase in the prevalence of TB in wild boar.

This modellingThe process, either mathematically or in the human brain, of creating an internal version of something that we can refer to, to better understand how it functions and our place within. Scientific modelling is where we take the best knowledge we have and build a version of what will happen, if we assume certain parameters. For example, we might model More reveals how introduction of a wild predator can not only stabilise increases in prey animals but radically reduce the impact of disease on domestic farming. There is some loss associated with predation of livestock by wolves. But this is more than made up for, by the reduction in disease mortality.

References

1. Richard J. Evans, Lorcán O’Toole & D. Philip Whitfield (2012): The history of eagles in Britain and Ireland:an ecological review of placename and documentary evidence from the last 1500 years, Bird Study, 59:3, 335-349
2. Tanner, E. et al. (2019) Wolves contribute to disease control in a multi-host system. Scientific Reports 9. https://www.nature.com/articles/s41598-019-44148-9.epdf

Spotlight

Research supported by The Born Free Foundation has established no scientific basis for killing badgers to prevent bovine tuberculosis.

Their analyses show that while the disease peaked and began to decline during the study period, there is no statistical evidence that the rate and nature of the decline was any different in the areas where badgers were being shot and the areas where there was no cull in place. The findings of the peer-reviewed study suggest that the slowing up and initial reduction of bovine TB in the High-Risk Area cannot be the result of badger culling and is in fact down to the progressive introduction of cattle-based measures including more intensive testing requirements and movement controls. The conclusions of the study are further supported by data from Wales, where a similar reduction in the disease has been achieved without culling badgers.

The work can be read in Veterinary Record.

Langton, TES, Jones, MW, McGill, I. Analysis of the impact of badger culling on bovine tuberculosis in cattle in the high-risk area of England, 2009–2020. Vet Rec. 2022;e1384. https://doi.org/10.1002/vetr.1384