Soil is part of the landscape, on the functions of which terrestrial life depends to a large extent. However, research on soil organisms has been very limited until recently, and most efforts have focused on "above-ground" organisms. A challenge for research is also the fact that it is often linked to trends observed in above-ground species, although life below the surface is influenced by different factors.
Earthworms are one of the important representatives of macroscopic soil fauna. At first glance, inconspicuous ringworms, whose activities affect not only the properties of the soil, but also the functioning and shape of entire ecosystems. It is not for nothing that earthworms are nicknamed "ecosystem engineers." However, the ability of earthworms to perform ecosystem functions depends, among other things, on their species composition and abundance. The knowledge of the ecology of earthworms is therefore absolutely essential for ability to predict how changes in their communities will affect the entire ecosystem. The first step towards a better understanding of earthworms was a study on global distribution and diversity from 2019 published in the journal Science, in which the scientist Radim Matula from the Faculty of Forestry and Wood Technology also participated. The aim of this study was to map and analyze global spatial trends in earthworm communities and identify natural factors that affect their biodiversity. The study was truly worldwide - data come from 6928 areas in 57 countries on all continents except Antarctica.
And what were the conclusions? The biggest surprise was the finding that the frequency and diversity of earthworms is not highest in the tropics and subtropics, as is the case with plants and above-ground animals, but on the contrary in temperate climates. The explanation may be, for example, the high rate of decomposition in tropical regions and the lower content of organic material in the soil with which the earthworms feed. The reasons for the surprisingly high species diversity of earthworms in medium latitudes are unclear. Glaciers have probably played an important role in the recent ice age, after which these areas were repopulated by species with a high ability to spread. In the tropics, where a similar phenomenon has not occurred, we encounter a smaller number of often highly endemic species, suggesting that earthworm ecosystem functions are limited and replaced by other soil species. Thus, it can be said that globally, climate is the most important factor influencing the diversity, abundance and biomass of earthworms. Within the individual climate regions (i.e. at the local level), other important variables appear, especially soil properties such as pH or carbon content, but also plant cover and many others.
The strong relationship between climate and earthworm communities is crucial, especially in the context of advancing climate change. It is in the temperate zone, where the abundance and diversity of earthworms is highest, that global warming can lead to disruption of key ecosystem functions. This would significantly affect the Czech Republic, which is one of the world's centers of earthworm biodiversity. This first global study emphasizes the importance of research on soil fauna, which has so far been often overlooked. Its inclusion in surveys could change the current view of the world's biodiversity centers and nature conservation priorities. The existing protected areas do not include the protection of earthworms or other soil organisms, which fundamentally affect the appearance of those areas.
Phillips H. R. P., et al. Global distribution of earthworm diversity. Science. 2019: 480-485
https://science.sciencemag.org/content/366/6464/480
Ing. Radim Matula, Ph.D.
Radim Matula works at the Department of Forest Ecology and has long been involved in the impacts of forest management, forest species composition and climate change on the diversity, productivity and stability of forest ecosystems. He is also currently building a global network of automatic sensors to monitor the effects of climate and variability on tree growth, stress and mortality.
Prepared by Dagmar Zádrapová