Urbanization Impoverishes Fauna, New Study Proofs

NL : https://www.eoswetenschap.eu/natuur-milieu/verstedelijking-verarmt-fauna

15/01/2020

post by Siska Van Parys

Urbanization reduces species diversity and decimates populations. That is the conclusion of a team of biologists after comparing a wide range of animal species between densely built-up and rural areas. The number of butterflies in densely built-up areas, for example, is up to 85% lower than in rural areas. 'Building more and more in rural areas impoverishes fauna,' says Frederik Hendrickx of the Royal Belgian Institute of Natural Sciences (RBINS).

With an average of 371 inhabitants per square kilometer, Belgium is one of the most urbanized countries in Europe. Also worldwide, the building frenzy is great and the built-up area is expected to triple between 2000 and 2030. Researchers have long suspected that converting natural and agricultural areas into urban environments has a negative effect on biodiversity. But to what extent, was not clear until now. 

Researchers from UCL, KU Leuven, UGent, UAntwerpen and RBINS have now systematically investigated this. They selected 27 areas - of 3 by 3 kilometers - in and around Ghent, Antwerp and Brussels: 9 rural, 9 semi-urban and 9 highly urbanized. And in each of these areas they selected 3 smaller zones - 200 by 200 meters - with different degrees of urbanization. In rural areas there are also village centers and within a metropolis there are also greener zones. This allows for a neat test whether urban nature has the same biodiversity as nature in the countryside.

The biologists systematically sampled those 81 selected sites with safety nets and traps, and examined ten invertebrate groups to see how abundant and species-rich they were. They examined rotifers (wheel animals), Cladocera (water fleas), butterflies, moths, spiders, ground beetles, crickets, grasshoppers and snails. 

First conclusion: the more densely built, the less numerous the spiders and insects. The impact is largest on butterflies: 85 percent fewer specimens compared to rural areas. 

Conclusion two: also species diversity is lower for most animal groups in more urbanized areas. 'Different urban locations more often contain the same species’, says Hendrickx, 'because only a limited number of species can thrive in urbanized areas. This results in a strong homogenization of the fauna.’

The impact of urbanization on the environment is complex. 'The main reason for the decline is most likely that the habitat of many species is continuously disturbed and fragmented’, says Hendrickx. There is also air, water and soil pollution, as well as light, scent and noise pollution. In addition, more densely built-up areas experience a different water regime due to the large amount of asphalt and concrete. These also retain heat, which results in a different microclimate in cities, the so-called heat island effect.

These typically urban living conditions homogenize the diversity of the fauna. Only species that are naturally adapted to a disturbed environment survive in urbanized areas. Hendrickx: 'That becomes clear when you look at the characteristics of the species that remain in the city. Only species that spread very well are able to colonize the disturbed environment over and over again and to build up populations there. Species that cannot spread by air over long distances are completely filtered out of the urbanized environment, resulting in a dramatic decline in species diversity'.

How can you halt the biodiversity loss through urbanization? The results suggest that a ‘brick stop’ and the preservation and protection of large connected areas of natural habitat is the most effective way. ‘Green space in the city is necessary to create a pleasant and healthier urban environment, but it does not appear to compensate for the loss of biodiversity due to urbanization. Urban planners should give priority to protecting and connecting natural habitat relics when developing the green infrastructure in the city', Hendrickx concludes.

The study was published in the journal Global Change Biology.