The mosquito has left the room and it is not something to be happy about
Last October, a group of entomologists from the Krefeld Entomological Society near Dusseldorf published a new study, where they announced an observed 75% decline in flying insects’ biomass over 27 years, in Germany’s protected areas. In about 3 decades, ¾ of German insect populations could have plummeted, with a mid-summer decline of 82%. The slump is independent of the habitat type, while changes in weather, land use, or habitat characteristics could not explain the overall decline, according to the authors.
Could these figures serve as an additional proof that we have entered the 6th extinction? In that sense, these last months have been hardly delightful: you might remember that in October 2016, a report from the World Wildlife Fund had announced that global populations of vertebrates had declined by 58% between 1970 and 2012; and if no immediate measure is undertaken, that this figure could reach 67% by 2020. In July 2017, three researchers from Stanford University and the UNAM (Mexico) published a study in PNAS about vertebrates where they demonstrated that the decline was “more severe than perceived when looking exclusively at species extinctions”, speaking about “biological annihilation”. Earlier, in May 2016, researchers from the USGS showed that the average decline in overall amphibian populations was about 4% per year; and in 2015, the ‘Living Blue Planet Report’ indicated that populations of fish species utilized by humans had fallen by half over 40 years. Now, it is the turn of insects to appear on the scene, so to say.
Biologists usually focus on the number of species to study the biodiversity crisis. However, analysing the populations in terms of species individuals or biomass, provides the advantage of giving a quantitative angle that fits basic ecological dynamics. Indeed, food webs mostly depend on quantity: a lower quantity of insects means first of all a lower quantity of food. Research suggests that it is not only the vulnerable species that are affected by the decline, but the whole flying insect community.
Insects play a major role in terrestrial food webs. Their disappearance poses a considerable risk to ecosystem services. These services include pollination, nutrient cycling, food provision to birds, mammals, amphibians, etc. According to the study, it is estimated that 80% of wild plants depend on insects for pollination, while 60% of birds rely on insects as a food source. J.E. Losey and M. Vaughan (Bioscience, 2006) state that the annual value of ecological services provided by wild insects in the United States could reach at least USD 57 billion. This figure constitutes however a floor value, as the study does not take systemic effects into account. A decline of this magnitude is expected to provoke cascading effects on food webs, which are hardly predictable.
Entomologists identified two prime suspects, landscape change and climate change, but failed to prove a statistical relation with local data. This would suggest that large-scale factors are involved, which is more alarming, as we could imagine a similar decline elsewhere in other countries. Agricultural intensification is another suspect that could not be considered in the analysis: in particular, the increasing use of pesticides (insecticides especially) is a probable explanation. Hereunder, pesticide and insecticide use evolution is presented. It should be noted that the quantity (in tonnes) of pesticide is an indicator that is limited, as the efficiency of molecules has been significantly improved over time.
This new evidence of an ecological collapse demonstrates the urgency of uncovering the specific causes, but most of all of engaging a radical shift in the way we consider development. Indeed, even if some uncertainty remains, it is quite clear that this crisis is anthropic, and that it is our economic model that must be reviewed. One of the keys in that sense is to include biophysical constraints into our models, as Beyond Ratings aims to do. Such a collapse requires to apply an extended precautionary approach, without waiting for irrefutable evidence.