Climate change: Fewer insects with earlier spring awakening
An earlier greening and blossoming of nature in spring can lead to fewer insects, especially in forests, according to a study. "Global warming is probably partly contributing to the dramatic decline in insects via this pathway," writes the research team from southern Germany in the journal "Communications Biology".
The cause lies in the interaction: if herbivorous insect larvae hatch well before the leaves emerge, they are in danger of starving to death. However, if they hatch well after, the food quality can be noticeably poorer because fresh leaves are the most digestible and richest in protein and often contain the fewest protective substances.
Leaf crowns tend to be denser
Another possible explanation is that the tree crowns tend to close up earlier when they turn green and shade the vegetation below - resulting in lower temperatures. According to the team, the results were less clear for other types of landscape such as meadows, fields and settlements.
The study investigated how the timing of the spring awakening is related to the number and diversity of insects in the year for around 180 locations in Bavaria. The scientists used satellite data from 2017 to 2019 as well as insect traps.
Further study shows correlation
A study presented in September also established a link between insect decline and climate change. According to the study, an accumulation of unfavorable weather conditions had a noticeable influence on the observed decline in flying insects in Germany in recent decades. The research team led by Jörg Müller from the University of Würzburg reported in the journal Nature that analyzed weather data was consistent with the decline in insect numbers.
However, the study was controversial among researchers. It was emphasized that the results should by no means be taken to mean that weather phenomena alone can explain the dramatic loss of insect biomass in recent decades. A major influence of the weather does not mean that other factors such as the use of pesticides and changes in land use do not also have a major influence.
Shrinkage of 75 percent
In 2017, a team led by Caspar Hallmann from Radboud University in Nijmegen (Netherlands) found a dramatic decline in the mass of flying insects in parts of Germany when analyzing data from entomologists in Krefeld. According to the study, the total mass decreased by more than 75 percent between 1989 and 2016. The main causes to date have been factors such as the intensification of agriculture and the loss of habitat.
Scientists from the Technical University of Munich (TUM) and the Universities of Würzburg, Bayreuth and Weihenstephan-Triesdorf were involved in the current study.
- The earlier greening of forests due to climate change might also impact forestry, as earlier leaf emergence could disrupt the life cycle of forest-dwelling insects, affecting their food source and resulting in potential population declines.
- The changing climate and seasons have been suggested as potential contributors to the observed decline in insect populations in various landscapes, such as meadows, fields, and settlements, as well as forests.
- The correlation between climate change, particularly the shifts in weather patterns such as early springs and extended dry periods, and the decline in insect populations has been highlighted in various studies, adding to the understanding of the complex factors impacting insect diversity and abundance.
Source: www.dpa.com
