Light pollution linked to decline in insects

A MAJOR factor in the rapid decline in flying insects over the past couple of decades is light pollution, say scientists.

Researchers have discovered that regions which have experienced a sharp decline in flying insects also have high levels of light pollution and say that along with climate change, pesticides and the change in land use, artificial light is a likely culprit.

Scientists from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries count insects as part of their research into rapidly declining numbers (Picture copyright Gabriel Singer/IGB)

Scientists from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Berlin were investigating the reasons why the biomass of flying insects has decreased by a staggering 75 per cent over the last 27 years, the  discovery of a previous study in 2017.

This was based on an analysis of trends in biomass of flying insects in selected protected areas within agricultural landscapes, and concluded that changes of climate and habitat are to blame for the decline in insect populations. But they pointed out that these impacts alone are unable to explain this drastic decline.

The Leibniz-Institute of Freshwater Ecology and Inland Fisheries team led by Dr. Maja Grubisic looked at the locations of the areas involved in the 2017 study: areas in conurbations that have a higher than average level of light pollution.

‘Half of all insect species are nocturnal,’ says Dr. Grubisic. ‘As such, they depend on darkness and natural light from the moon and stars for orientation and movement or to escape from predators, and to go about their nightly tasks of seeking food and reproducing.

‘An artificially-lit night disturbs this natural behaviour and has a negative impact on their chances of survival.’

The scientists analysed all recent studies on the effects of artificial light at night on insects, and found that there is strong evidence to suggest a credible link between light pollution and declines in insect populations.

For example, flying insects are attracted by artificial lights - and, at the same time, are removed from other ecosystems - and die from exhaustion or as easy prey.

Additionally, rows of light prevent flying insects from spreading; causing a lack of genetic exchange within fragmented insect populations that could reduce their resistance to other negative environmental influences, which are especially pronounced in agrarian areas.

A decline in insect populations in agricultural areas - which make up no less than 11 per cent of land use worldwide - does not only mean a decline in species diversity, but also jeopardises important ecosystem services: for example, there are then fewer moths, beetles and flies to pollinate plants. Also, changes in the occurrence and behaviour of pests such as aphids or their enemies such as beetles and spiders can disturb the balance of this well-tuned system.

Furthermore, artificial light at night may also have a direct impact on the growth and flowering time of plants, and therefore on yield.

‘Our overview study shows that artificial light at night is widely present and can have complex impacts in agricultural areas, with unknown consequences for biodiversity and crop production,’ Dr. Franz Hoelker, head of the Light Pollution and Ecophysiology research group at IGB, told Lux. ‘Therefore light pollution should be generally considered as a potential ecosystem disturbance in future studies to identify ways in which practical steps can be taken to reduce environmental concerns.’

 

  • Read the full paper HERE.

 

  • Light pollution is one of the topics at the Safer Cities conference taking place at the LuxLive 2018 exhibition and conference at ExCeL London on Wednesday 14 November and Thursday 15 November 2018. For more information, and to register, click HERE.

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Other studies have shown that increased road traffic has had major impacts on insect population. Citing a 25% decline. "Flying insect abundance declines with increasing road traffic" First published: 16 May 2018 https://doi.org/10.1111/icad.12300 A lot of "science" these days seems to be designed to prove a hypothesis, and does not seem to engage in balanced research. There is quite a big leap between "partly to blame" and a "major factor". Other factors cited in other papers is pesticide use and nitrogen fertilizer and increasing urbanization. The lighting industry needs to be careful in its claims or it risks the "cry wolf" syndrome.

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