Covid-19. What impact does lockdown have on biodiversity?

Nathalie Machon is a specialist in urban ecology at the Centre d'écologie et des sciences de la conservation¹  works in conjunction with the Institut de la transition environnementale at Sorbonne University. She looks back on the impact these two months have had on urban biodiversity. 

What observations did you make about wildlife in the city during lockdown? 

Nathalie Machon : In these two months, vegetation has made a comeback in public spaces. This does not mean that there was a greater diversity of species, but that those already in place were much more visible than usual because they were not being cut down. 

In terms of wildlife, we have seen some wild animals take advantage of the sudden slowdown in human activities to venture into cities: deer in private gardens, wild boars on the Croisette in Cannes, dolphins in Italian ports, whales in the calanques of Marseille, seals on the beaches of Dunkirk, etc. Although animals have been more visible than usual, I do not nevertheless believe that the lockdown had a great impact on their population because it was too brief.  

What methods do you use to observe this biodiversity?  

N. M. : Studies are based on inventories. When they concern large areas or extend over long periods of time, we call on volunteers who can provide us with information about what is happening around their homes. This is the objective of the Vigie-Nature participatory science program run by the Natural History Museum and the Sorbonne University Alliance. Based on simple and rigorous protocols, it offers everyone the opportunity to contribute to research by discovering biodiversity through different projects: "The Garden Biodiversity Observatory", "Lichens go!", "Sauvages de ma rue", etc. 

From the observations submitted by volunteers on the flora and fauna, we can draw up syntheses and see what links exist between biodiversity, human practices and the structure of the city. With the lockdown, the amount of data collected decreased, as outputs were limited: we received 660 data compared to the usual 3000 to 4000. We hope that with the easing of the lockdown, it will resume. 

What conclusions can be drawn about the impact of the lockdown on biodiversity? 

N. M. : It is still too early to draw conclusions, but I don't think the impact has been huge. With the interruption of mowing in public spaces, one can imagine that some plant species, usually cut short before they have even produced flowers, fruits and seeds, have been 
preserved during these two months. They may therefore be more present next year, even though the drought in April may have prevented some plants from growing. 

By no longer mowing and clipping flora on the public highway during the lockdown, we also protected a number of insects that lived there and allowed them to complete their natural cycle. The increase in the number of insects means more food for the birds, while allowing vegetation to grow might also lead to more snails in plants and therefore more food for hedgehogs, which have been less affected by traffic during lockdown. 

Moreover, although hunting was partially authorised in some places to protect crops, there were fewer hunters overall during this period. This is likely to have an impact on some animal populations.  

But there is a quid pro quo for all this. For it is likely that, during those two months, many people mowed more, weeded more and used their stocks of plant protection products in their private gardens.    

What measures put in place during lockdown do you think should be continued to protect biodiversity?  

N. M. : Generally speaking, we must take reasonable action on biodiversity and leave more room for green spaces, including on public roads. Instead of covering everything with concrete, it would be interesting to let plants grow on areas such as roundabouts, car parks, or to plant roofs or façades. It would also be a good idea to reduce mowing between April and June to allow species to complete their natural cycle.

I hope that this pause linked to lockdown will have made city dwellers aware of the importance of biodiversity. They have been able to see verdant public spaces and realise that, even if we do not mow, if we do not uproot, if we do not shear, it’s nice to see wild flowers in spring growing on the slopes. Perhaps they will want this urban flora to be managed in a less drastic way. 

What are the risks to biodiversity with the progressive easing of the lockdown? 

N. M. :The abrupt reconquest of space by humans may be painful for species that had felt more confident with the decline in activity, noise and cars. This is particularly true for animals born at the end of winter and which had not yet experienced anything of human aggression.  

What role does urban biodiversity play for city dwellers? 

N. M. : Beyond the mental and physical well-being it provides, vegetation has a real use in the city. It absorbs some of the greenhouse gases and pollutants from the soil, air and water and regulates the temperature during heat waves. In the summer of 2003, the mortality rate was significantly higher in neighbourhoods without vegetation.   

It also has a direct impact on our health. It has, for example, been shown that children suffer less from allergies in green neighbourhoods than elsewhere, as the great diversity of plants makes it possible to dilute allergenic pollens (such as those from lawns). 

People have learnt that they need nature and they are now ready to give it a chance. Mentalities are changing and we are no longer faced with the city of yesteryear where every blade of grass needed to be cut. In fact, since use of plant protection products ceased in public spaces, the urban ecosystem is the only ecosystem on the planet that is in better shape now than it was a few years ago.  

¹ CESCO (Sorbonne University/Museum of Natural History/CNRS)