Above us only sky -- The open air as an underappreciated habitat

May 17, 2018

Numerous bat species hunt and migrate at great altitudes. Yet the open sky had, until recently, not been on the radar of conservation scientists as a habitat relevant to a large variety of species. Christian Voigt and colleagues from the Leibniz Institute for Zoo and Wildlife Research (IZW) in Berlin have collated the current scientific knowledge on potential hazards to one group of animals flying at high altitudes, bats. In their recent article published in BioScience the authors synthesise threats facing bats in troposphere and provide recommendations for potential protective measures to ensure persistence of bats and other high-flying animals.

Bats reach surprising altitudes while out on their nightly hunt. They utilise a large area to forage, stretching from the treetops to the lower troposphere. Bats have been recorded using onboard GPS loggers at heights of 500 metres above the ground in Germany, reaching up to 800 metres in Thailand. Yet the current record holder is the Mexican free-tailed bat Tadarida brasiliensis which has been recorded at the lofty height of 3000 meters above the ground! Even species like the common noctule Nyctalus noctula, inhabiting much of Europe, can reach altitudes above 1000 metres. Thus the high altitudes are an underappreciated habitat for bats and this region has largely been ignored in species conservation efforts. There are currently no specific policies or concepts for aeroconservation in Europe even though 21 of the 53 bat species native to the continent hunt for insects in these open spaces.

"When we think of the term habitat we generally think about features in the landscape: meadows, forests, or bodies of water, and other earth surfaces", says Christian Voigt. "The lower boundaries of the troposphere escape our attention as a habitat relevant and important to animals." Yet they are full of life. Both birds of passage and many insect species migrate at high altitudes. "Insects use winds to cover distances that they would not manage on their own." It's no surprise that bats use this open space: It's where their food is.

Insect density varies by region. Their numbers have also generally declined due to air pollution and the increased use of pesticides across the globe. Voigt and colleagues estimate that to bats the open sky is further fragmented into 'food-rich' and 'food-poor' zones. Large clouds of bats in South East Asia can, depending on the species, cover distances of up to 40 or 50 kilometres during their nightly foraging. Analysis of radar data from North America illustrates that they span out in all three dimensions covering large swathes of land. "Some bat colonies consist of one, two, or even ten million individuals. Not all of them can locate their prey nearby and they have to utilise high altitudes. There they also feed on insects harmful to human agriculture", Christian Voigt explains.

The animals are exposed to a variety of threats while hunting in the open air. Collisions with anthropogenic structures like high buildings, wind-power farms, drones, helicopters, and airplanes are direct impacts of human activity causing injuries and potentially death. With the increasing volume of air traffic and utilisation of wind energy sources this human influence is a growing threat.

Aside from reduced insect density, indirect impacts include light and air pollution, like dust and chemical pollutants, and exhaust fumes all of which can result in impaired health and reduced reproductive fitness. "Bats are winged athletes. We have observed two species which ascended and descended several hundred metres repeatedly in a very short timeframe. To do so requires immense effort, leaving the animal potentially highly vulnerable to air pollutants", Voigt emphasised. In addition, as nocturnal animals bats are highly sensitive to light pollution and the relationship between bats and artificial light at night has yet to be determined at such high altitudes.

Protecting the open sky is far more difficult than conserving clearly defined terrestrial and aquatic habitats. "It is, basically, the same predicament as with the oceans. The open sky is in public hands and common property which makes accountabilities harder to disentangle, and controls difficult to enforce", says Christian Voigt. Bats are the only mammals capable of flight. Next to their immediate worthiness of protection, bat conservation is also of direct economic interest to humans as bats provide agricultural pest control services across the world.

A number of practical aeroconservation approaches do already exist. "A variety of long-lasting protection strategies have been developed. In Germany, at least, wind power plant operators have to comply with a variety of permit requirements that are designed to limit bat and bird casualties. Unfortunately, how well these are implemented, across the country, is currently unknown", says Voigt. The migration corridors and roosting and resting areas of bats and birds have to be kept free of wind power plants. Strategies to reduce the impact of light emission and sky glow to bats are simple and efficient. Focus light toward the ground and limit light spill toward the sky! Voigt and colleagues urge for an expansion of research into the troposphere as an essential habitat as it is crucial for us to understand how the animals that exist in these open spaces can best be protected.
-end-


Forschungsverbund Berlin

Related Air Pollution Articles from Brightsurf:

How air pollution affects homeless populations
When air quality worsens, either from the smoke and ozone of summer or the inversion of winter, most of us stay indoors.

Exploring the neurological impact of air pollution
Air pollution has become a fact of modern life, with a majority of the global population facing chronic exposure.

Spotting air pollution with satellites, better than ever before
Researchers from Duke University have devised a method for estimating the air quality over a small patch of land using nothing but satellite imagery and weather conditions.

Exposure to air pollution during pregnancy is associated with growth delays
A new study by the Barcelona Institute for Global Health (ISGlobal) has found an association between exposure to air pollution during pregnancy and delays in physical growth in the early years after birth.

Nearly half of US breathing unhealthy air; record-breaking air pollution in nine cities
Amid the COVID-19 pandemic, the impact of air pollution on lung health is of heightened concern.

Air pollution linked to dementia and cardiovascular disease
People continuously exposed to air pollution are at increased risk of dementia, especially if they also suffer from cardiovascular diseases, according to a study at Karolinska Institutet in Sweden published in the journal JAMA Neurology.

New framework will help decide which trees are best in the fight against air pollution
A study from the University of Surrey has provided a comprehensive guide on which tree species are best for combating air pollution that originates from our roads -- along with suggestions for how to plant these green barriers to get the best results.

Air pollution is one of the world's most dangerous health risks
Researchers calculate that the effects of air pollution shorten the lives of people around the world by an average of almost three years.

The world faces an air pollution 'pandemic'
Air pollution is responsible for shortening people's lives worldwide on a scale far greater than wars and other forms of violence, parasitic and insect-born diseases such as malaria, HIV/AIDS and smoking, according to a study published in Cardiovascular Research.

Air pollution in childhood linked to schizophrenia
Children who grow up in areas with heavy air pollution have a higher risk of developing schizophrenia.

Read More: Air Pollution News and Air Pollution Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.