Climate change is an undeniable reality, and while natural climate variations have occurred over millennia, the current pace of change exceeds natural expectations, primarily due to human activities. The most noticeable changes are in the levels of carbon dioxide, temperature and rainfall. These changes will not be the same everywhere. For example, some areas are predicted to have less rainfall (like southern Africa), while others will witness increased precipitation. Temperature is also expected to rise by 1.5°C (best-case scenario) to 4°C (most pessimistic scenario) by 2100, with variations across different geographical locations. These changes in our climate will have profound consequences for all life on our planet, including soil-dwelling invertebrates.
Soil invertebrates, such as mites (Fig. 1) and springtails, play essential roles in ecosystem functions such as breaking down organic matter and partaking in the intricate soil food web. They depend on the right soil temperature and moisture levels to thrive. Additionally, changes in carbon dioxide levels can indirectly impact them by altering the plant assemblages they rely on. When the temperature and moisture conditions shift, it can cause problems for the ecosystem and affect how quickly organic matter is broken down in the soil.
To understand how climate change is impacting soil invertebrates, scientists use experiments where they can manipulate the climate on a small scale to see what may happen in the future. It’s like making a mini version of the Earth’s future and comparing it to how things proceed in the current natural world. One effective tool researchers use is something called an open-top chamber. These chambers can be small and cover just a few plants (Fig. 2) or be huge and enclose entire trees in a forest (Fig. 3). They are like clear plastic boxes with no roof, so the sunlight can get in and warm things up, but they also allow for natural rainfall. Some chambers even have heating coils buried under the soil to make the environment even warmer. For studying both warming and higher carbon dioxide levels, scientists use chambers that release extra carbon dioxide. Closed-top chambers are used to test how warming and drying affect animals inside. Some modifications use clear sheets with open sides to let the wind, carbon dioxide and humidity in, but still reduce rainfall and increase temperature (Fig. 4). These experiments can last from just a few months to as long as 20 years. Researchers collect soil samples with invertebrates from inside these chambers and compare them to samples from outside, which serve as a control group.
Scientists have done a lot of these experiments around the world, and in a meta-analysis of 86 of these experiments it has been found that overall the soil invertebrate system seems quite stable; however, the results differ depending on the type of experiment, geographic location and many other variables. In general, when it gets warmer and drier, there tend to be fewer springtails. However, mites can respond in many ways in different places. Surprisingly, no studies from Africa have been identified in this analysis (Fig. 5). The closest study has been done on Marion Island, which is experiencing significant climate changes. Over the last 60 years, the annual rainfall on Marion Island has decreased by 25 mm, while annual air temperatures have increased by 1.2°C. This study focused on a cushion plant inhabited by soil invertebrates, revealing that after one year, the mite population density increased under the dry-warm treatment, while the springtail density decreased. It also showed that different species responded to the changes each in their own way, highlighting the need to study individual species.
Such experiments help us understand how climate change affects soil invertebrates. More studies, especially in Africa, will help us get a better picture of what’s happening to the soil ecosystem as our climate keeps changing.
References
Barreto, C., Conceição, P.H.S., de Lima, E.C.A., Stievano, L.C., Zeppelini, D., Kolka, R.K., Hanson, P.J.& Lindo, Z. 2023. Large-scale experimental warming reduces soil faunal biodiversity through peatland drying. Frontiers in Environmental Science, 11, Art. 1153683. https://doi.org/10.3389/fenvs.2023.1153683
Goncharov, A.A., Leonov, V.D., Rozanova, O.L., Semenina, E.E., Tsurikov, S.M., Uvarov, A.V., Zuev, A.G.& Tiunov, A.V. 2023. A meta-analysis suggests climate change shifts the structure of regional communities of soil invertebrates. Soil Biology and Biochemistry, 181, Art. 109014. https://doi.org/10.1016/j.soilbio.2023.109014
Intergovernmental Panel on Climate Change [IPCC]. 2023. IPCC Press Release: Urgent climate action can secure a liveable future for all. 2023/06/PR. Geneva, Switzerland: IPCC, 4 pp. https://www.ipcc.ch/report/ar6/syr/downloads/press/IPCC_AR6_SYR_PressRelease_en.pdf
McGeoch, M.A., Le Roux, P.C., Hugo, E.A. & Chown, S.L. 2006. Species and community responses to short-term climate manipulation: Microarthropods in the sub-Antarctic. Austral Ecology, 31, 719-731. https://doi.org/10.1111/j.1442-9993.2006.01614.x
Meehan, M.L., Barreto, C., Turnbull, M.S., Bradley, R.L., Bellenger, J.-P., Darnajoux, R. & Lindo, Z. 2020. Response of soil fauna to simulated global change factors depends on ambient climate conditions. Pedobiologia, 83, Art. 150672. https://doi.org/10.1016/j.pedobi.2020.150672
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