South Africa’s cave-dwelling bats need more protection – to keep people safe too

The landscape immediately surrounding a cave is important to bats too. The animals usually hunt and find water to drink within a 5km radius of their home caves. So, any destruction of a cave and its surrounds will have major consequences for local bat populations. That, in turn, is bad news for ecosystems. Bats are critical components of a healthy environment: fruit-eating bats pollinate flowers and spread seeds, while insect-eating bats control insect populations like flies and mosquitoes.

The destruction of natural habitats brings humans into closer contact with wild animals, such as bats, which may lead to future outbreaks of zoonotic diseases – those of animal origin. When natural habitats are destroyed, animals like bats need to find new places to live; those that can adapt will likely move into buildings. Others may simply not survive.

Many caves around the world are threatened by human activities – vandalism, pollution and illegal mining of non-renewable sediment deposits such as limestone. They’re also at risk from land-cover changes such as increasing urban settlements, expanding agriculture and extensive groundwater extraction.

Despite this, most are not formally protected under conservation laws. In South Africa, for instance, much of the current focus on caves falls primarily on their significance as fossil sites; no formal cave conservation plans currently exist.

My colleagues and I from the Centre for Viral Zoonoses in collaboration with the Mammal Research Institute at the University of Pretoria investigated the state of the landscape around 47 important bat caves in South Africa. Our findings were fairly dire. Between 2014 and 2018, tree land cover decreased by 4.26% around all the caves, while urban and agricultural land cover increased. The distances between urban areas and caves also decreased in this period; the average distance for all caves to the nearest urban settlements was 4.15km in 2018, an average decrease of 0.17 km from 2014. This means there’s less distance between humans and bats.

Cave-specific conservation and protection actions are essential to protect cave habitats for the continued survival of bats and, ultimately, the wellbeing of humans.

Unpacking the data

South Africa is home to more than 60 bat species, at least 18% of which rely on caves for their survival.

Two species, the Natal long-fingered bat and the Egyptian Rousette bat are probably the most numerous and widespread throughout the country. These species often live in the same caves; both are earmarked for long-term surveillance by our research group because they are hosts for a variety of viruses.

We used a cave database that I compiled for my PhD for the two species. This gave us 47 locations of caves throughout the country. Using two publicly available land-use change maps from 2014 and 2018, obtained from the Department of Environmental Affairs, we investigated the degree of land cover change for eight different land-cover classes – trees, other vegetation, urban settlements, agriculture, bare ground, plantations and wetlands – within a 5km radius of all 47 caves. We also compared the distances between caves and the nearest urban settlements between the two dates.

Lastly, we compared cave localities with the South African National Biodiversity Institute’s 2018 National Biodiversity Assessment and Ecosystem Threat Status map, to determine the protection level for the ecosystems where caves were located. Ecosystems on this map were classified as not protected, poorly protected, hardly protected, moderately protected and well protected. This depended on the proportion of each ecosystem type that remained in a good ecological condition.

How landcover around caves changed between 2014 and 2018. Image: Dr Mariette Pretorius / Supplied