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80 % of European insects have disappeared in thirty years

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This is the most massive episode of species extinction since the disappearance of the dinosaurs. More than half of all insects are disappearing worldwide at an accelerated rate; the hecatomb is reaching the staggering figure of 80 % for Europe. When insects disappear, the entire living chain is affected. More food for birds dying en masse, fewer pollinators for key food crops. A frightening assessment in a synthesis of 73 studies pointing to the responsibility of intensive agriculture in this collapse of life.
 
Pith nearly half of the world's insect species, essential to ecosystems and economies, in rapid decline, warns a study published in the journal Biological Conservationwhich warns of a "catastrophic collapse" of the natural environment. « The conclusion is clear: unless we change the way we produce our food, insects will be on the road to extinction within a few decades. "The authors of this "frightening" review, a synthesis of 73 studies, which points in particular to the role of intensive agriculture, point out.
 

The most massive extinction episode since the disappearance of the dinosaurs...

Today, about a third of all species are threatened with extinction." and each year approximately 1% is added to the list ", calculated Francisco Sanchez-Bayo and Kris Wyckhuys of the universities of Sydney and Queensland. This equates, they note, " to the most massive extinction event "since the disappearance of the dinosaurs. "The proportion of declining insect species (41%) is twice as high as that of vertebrates and the rate of extinction of local species (10%) is eight times higher. "they point out.
 
Philippe Grandcolas, director of research at the CNRS, confesses, in a post of The Conversation, depressed on reading this study because it sheds light on a series of catastrophic cases concerning butterflies, hymenoptera (bees, wasps, ants), beetles (ground beetles, beetles, ladybirds, etc.), dragonflies and other groups of insects that are less charismatic but just as indispensable to biodiversity, such as pearls or mayflies. And this in many regions and different types of environments.
 

Vital to global ecosystems

When we talk about biodiversity loss, the fate of large animals often captures attention. But insects are " of vital importance for global ecosystems » : « such an event cannot be ignored and should prompt action to prevent a catastrophic collapse of natural ecosystems ", the scientists insist in their conclusions.
 
An example of the vital service provided by insects, and probably the best known, is the pollination of crops.
Conversely, an example of the impact of their disappearance on the entire food chain: the "vertiginous" decline in rural birds revealed in France in 2018. « We're almost out of bugs, that's problem number one. As one of the authors of the French study, Vincent Bretagnolle, explained at the time: "Because even granivorous birds need insects at some point in the year for their chicks...".
 

Butterflies, ladybugs, ants...

According to a study published at the end of 2017 and based on catches made in Germany, Europe would have lost nearly 80% of its insects in less than 30 years, contributing to the disappearance of more than 400 million birds. Birds, but also hedgehogs, lizards, amphibians, fish... all depend on this food.
 
Australian researchers point to the loss of insect habitat (urbanization, deforestation, agricultural conversion) and the use of synthetic pesticides and fertilizers as the main causes of the decline in insects, at the heart of the intensification of agricultural practices over the last 60 years.
Philippe Grandcolas points out that the diversity of studies listed in the Biological Conservation article clearly establishes four main causes responsible for the decline of insects: conversion of natural environments (agriculture and urbanization, loss of landscape and wetland diversity), pollutants - whether fertilizers or pesticides, bearing in mind that most pesticides are insecticides -, biological factors (introduction of pathogens, invasive species or pseudo-auxiliaries) and, finally, climate change.
 
The study is based in particular on the cases of Europe and the United States, where the most regular follow-ups are available. « But since these factors apply to all countries of the world, insects should not fare differently in tropical and developing countries. ".
In addition to these reasons are pathogens (viruses, parasites), invasive species and finally climate change, but especially at this stage in tropical regions.
 

An accelerating retreat

The decline of insects, which make up two-thirds of terrestrial species, dates back to the early 20th century, but accelerated in the 1950s and 1960s to reach "alarming proportions" in the last 20 years.
Among the most affected are lepidoptera (butterflies), hymenoptera (bees, wasps, ants, hornets... present on all continents except Antarctica) and beetles (beetles, ladybirds).
Some 60% of dung beetle species are thus in decline in the Mediterranean basin. And one in six species of bees has disappeared regionally, worldwide.
Aquatic insects are not spared, whether dragonflies or mayflies.
 
Restoring habitats and rethinking agricultural practices, in particular by seriously curbing the use of pesticides and replacing them with more sustainable practices, are urgently needed. "The report's authors also call for the clean-up of polluted water in both urban and rural areas. Philippe Grandcolas adds that the correlation between the number of insects and the bird populations that depend on them for food is well known. We also know the fundamental role of pollinating insects. But we must also imagine the complexity of the interaction networks between the 40,000 species of insects, the 8,000 or so species of plants and the hundreds of species of vertebrates present in metropolitan France. While we now know these networks, and in particular the flows that pass through them, we know much less about the effects of these declines at finer local levels. On the other hand, some of the consequences may be counter-intuitive: the disappearance of rare and scarce species can have significant effects given their key role in ecosystems.
 
The mass extinction of insects seems to be taking an unstoppable turn. Yet, according to Philippe Grandcolas, it is still possible to act: " An indispensable diversity of landscapes should be immediately restored, and a massive practice of sustainable, even organic, agriculture should be practised, in which biological control and good practices can significantly reduce the use of inputs. "If this solution is well known, its rapid implementation unfortunately still seems to depend on the weakness and procrastination of decision-makers and the weight of lobbies and economic actors who only think of short-term profitability to the detriment of everything else.
 
 
Sources: AFP, The Conversation
 

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