The other side of the current insect extinction: Exotic species increase through human impact

Various scientific studies have warned of a global decline in the abundance and diversity of insects. These studies have been carried out mainly on the European and North American continents, with other regions, such as islands, have been less studied.

This in mind, an international research team from Portugal, France, and Finland studied the insects captured over six years in the native forests of Terceira island, the Azores.

The results revealed that the diversity of exotic species of arthropods increased with time. Exotic species have been introduced into the archipelago consciously or inadvertently through economic activities.

"A greater diversity of exotic species may imply a change in various types of ecosystem services, disrupting processes such as predation and recycling of nutrients," says Paulo Borges, researcher at the at the University of the Azores, Portugal.

In the Azores, exotic species have their maximum abundance and diversity in habitats created by man.

"The fragmentation of native habitats and the proximity of some of these non-native habitats is promoting a flow of exotic species to the native forest. The process seems to be increasing in recent years possibly due to the combination of climate change and degradation of the native forest due to the spread of invasive plants," explains Pedro Cardoso, curator at the Finnish Museum of Natural History Luomus, University of Helsinki, Finland.

The study also shows a slight decrease in the abundance of island species that are not found anywhere else on the planet, such as the Azorean money spider (Savigniorrhipis acoreensis), which occurs on all the archipelago with the exception of Corvo island.

The study took place between 2013 and 2018. During that time, 30 thousand arthropods were captured in the native forest of Terceira. The insects collected corresponded to 159 species, 32 of which are endemic.