COVID19: the anthropause will not happen

Do you remember that end-of-the-world atmosphere during the first lockdown? A large part of humanity was under house arrest, and in many places nature was reclaiming its rights. Ecologists call this strange phase of our history the ‘anthropause’, especially in reference to the collapse of air traffic in the spring of 2020: global energy consumption fell by 6% last year. Like many people, I said to myself, “this is it, the industrialised nations are finally going to change their ways of doing things, to review their relationship with nature”.

One year and four million deaths later, I am less optimistic. Of course, the wilderness will have gained some respite, but beyond all the human tragedies, the ecological balance of the pandemic will be negative. Locally, successive confinements have facilitated a relaxation of environmental standards in the name of maintaining production, and the lack of controls has encouraged fraud. Industrial agriculture, deep-sea fishing, logging and construction have gone into plundering mode, while the state, bogged down in crisis management, neglects the surveillance of protected areas and has given up on respecting the environmental code. This same state is losing sight of the ecological transition, while public opinion is ready, and is severely repressing alternative attempts. At the European level, decision-makers remain unmoved, as illustrated by the recent debates on the Common Agricultural Policy and fisheries: while the modalities of agroecology and fisheries ecology are well known and would allow for the necessary transitions towards more environmentally friendly practices, the recovery plans support ecologically and socially damaging operating modes. On a global scale, it is now clear that the pandemic will exacerbate poverty and the already scandalous inequalities between social groups and nations. It is anticipated that the crisis will push at least 150 million more people into extreme poverty and worsen the status of women, particularly in urban areas of sub-Saharan Africa and Asia.
As we sink back into a consumer frenzy in the wake of deconfinements, and as our economic systems pursue illusory and deadly growth, ecological research reminds us that everything is linked: environmental destruction, health and economic crises, and social tensions; with dizzying global geopolitical consequences.

Helping each other to the top

The legionary ants are making rapid progress, hunting down their prey. Cockroaches, beetles, scorpions and tarantulas are all targets. Even lizards, snakes and small birds are attacked. Captured animals are stung, cut up and carried back to the bivouac, an aggregation of ants sometimes a hundred metres away.

In the forests of Panama, a bivouac of army ants can contain two million individuals. In order to feed them, the voracious larvae and the queen they protect, an efficient supply chain must be established. Long columns of legionnaires thus roam the ground. They consist of a caste whose sole function is to transport food, at the speed of ten body lengths per second (60 km/h in a 1.7 m human). These 5 mm creatures are the fastest of all ants, but sometimes they have to cross obstacles. When a bridge is needed, the legionnaires cluster at each end of the precipice until it is filled in, in a garland of bodies. If the column has to cross a very steep area, some ants stop in the middle of the slope and dig their claws into the substrate. In this way, the individuals become an animal ladder, a scaffold that fellow ants climb at full speed.

Is this altruistic behaviour governed by a collective organisation? In order to better understand this, colleagues (1) set up a small experiment, and a lot of mathematical models. In the path of a column of army ants, they installed a board whose inclination they could vary. The agile creatures tolerated slopes five times steeper than the steepest French departmental road, but beyond this threshold they built a scaffold in 80% of cases. This allowed them to cross even a vertical wall. The researchers believe that even if the benefit of scaffolding is collective, the decision to put it up is individual: the ant fixes itself to the slope when it notices that it or its neighbours are slipping, without waiting for an order from some headquarters. The scaffold-building legionnaires would therefore not use chemical communication, as they do when they capture a large prey. In this other case, the ants emit pheromones that attract a large number of conspecifics from the bivouac in order to take advantage of an abundant resource.

It is often assumed that coordinated animal behaviour requires thought and communication. In army ants, recent research indicates that movement in the forest remains rapid and fluid due to individual reflexes in favour of a common good. This high level of responsiveness increases the resilience of the small world of social insects; its ability to overcome obstacles and upheavals.

(1) Lutz, M. J., Reid, C. R., Lustri, C. J., Kao, A. B., Garnier, S., & Couzin, I. D. (2021). Individual error correction drives responsive self-assembly of army ant scaffolds. Proceedings of the National Academy of Sciences, 118(17).

Army ants (Ch’ien Lee/Minden Pictures/Biosphoto)

Nectar from urban gardens to the rescue of insects

A sunny spring day in the Deux-Sèvres. In my garden, bees and bumblebees are buzzing. Just on the other side of the dry stone wall, the agricultural plot is silent. Populations of pollinating insects are collapsing in Western Europe, mainly due to lack of food. Are populated areas refuges for all the little beasts?

Colleagues (1) investigated this question in 12 locations in the UK, comparing the amount of nectar produced by flowers in cities, agricultural areas and protected areas. To do this, they collected as much nectar as possible from the different flowers with a micropipette, becoming foragers themselves.  To their great surprise, there was on average no more nectar available for insects in the city than in agricultural areas and protected areas. However, within urban areas, some fully concreted habitats were extremely poor, while home gardens produced 85% of all available nectar, four times more than public parks. Thus, insects have much more food available to them in a garden than on an agricultural area. This urban nectar comes from a wide variety of plants, which contributes to its quality and extends the period of the year during which it is available. The second surprise was that 83% of the nectar in the gardens was produced by exotic plants. These species are often considered to be “beautiful and useless”, as they do little to benefit local biodiversity. Some are even invasive and potentially harmful. In fact, the study by British academics indicates that exotic flowering plants may have become essential for the survival of insects in our urban landscapes. Of the 536 flowering plants they studied, the scientists point out that species such as borage and butterfly tree (from the Middle East and China respectively) are excellent sources of nectar. For public parks, they recommend reserving certain areas to grow mixed flowers, which produce 16 times more nectar than a lawn.

This study is sure to delight urban gardeners, where flowering plants are now taking on a militant air; I’ll be thinking of them as I watch the bees foraging in the borage beds that bloom on the edge of my vegetable garden.

(1) Tew, N. E., Memmott, J., Vaughan, I. P., Bird, S., Stone, G. N., Potts, S. G., & Baldock, K. C. (2021). Quantifying nectar production by flowering plants in urban and rural landscapes. Journal of Ecology 109: 1747-1757.

Bombus pascuorum (Photo credit: Getty)

In the cool of the air conditioning

Phoenix, Arizona, the hottest city in the United States. Three months of the year, the daytime temperature exceeds 40°C. Since the invention of air conditioning a century ago, wealthy humans have lived in a cool bubble. Around them, animals are increasingly roasting in the Arizona sun as urban activity creates a deadly heat island; even rattlesnakes are fleeing.

More than 100 bird species are threatened by climate change in Arizona, but rosy-faced lovebirds found a trick. These small, colourful parrots have come a long way; their ancestors were captured in southern Africa, and shipped to American pet shops. Some escaped and, from the 1980s, an urban population settled in Phoenix. Several thousand now live in the metropolis, colonising the palm trees and cacti of the most wooded gardens, in place of the dry forests and savannahs of their origins. For the past decade, researchers at Arizona State University have seen them indulge in a strange activity. On the hottest afternoons between June and October, the lovebirds perch on the air vents of some buildings. At first sight, this does not seem to be a good idea, as one can imagine these ducts pulsating with the overheated air of air-conditioning units. Perching on these giant hairdryers would therefore be appropriate in winter, as European magpies do on some chimneys, but not during a heat wave. The puzzled researchers turned to the university’s technical services and solved the puzzle: the system in question dates back to the 1960s, when oil orgies made it possible to spend lavishly, including on artificially cooled air. Thus, the air vents frequented by the cute parrots are used to ventilate rooms cooled by air conditioners, evacuating deliciously cool air. The lovebirds literally queue up to swoon, as we open a fridge in the middle of a heatwave to catch a bit of freshness.

Why only these birds from elsewhere have figured out the trick? It is surprising not to see local creatures, such as mockingbirds and hummingbirds, also visiting the cooling vents. Of course, the manoeuvre is very technical as they have to perch on particularly slippery metal slats, with all the skill and intelligence of a parrot to stay on them. But there is more: the immigrants are intrepid and inventive. Where local species are content to endure the relentless heat, newcomers adapt and persist.

Reference: Mills, R., & McGraw, K. J. (2021). Cool birds: facultative use by an introduced species of mechanical air conditioning systems during extremely hot outdoor conditions. Biology Letters, 17(3), 20200813.

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