When novel organisms change to a new habitat, they could encourage the ecological balance that has been formed over a long time. Herbivores and plants are categorised by long-term co-evolution, which has formed not only their geographic distribution but also the features that they show in their habitats.
At higher advancements, insect herbivores are less plentiful in general, leading to plants being less well-protected against herbivores, due to quicker growing seasons and lower energy.
Besides, plant species natural to lower raises safeguard themselves against more varied and plentiful herbivores by having thorns or hair, spikes, or toxic substances. This environmental organization could be affected by climate change.
Grasshoppers Translocated to High Elevations
Scientists from ETH Zürich, the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), and the University of Neuchâtel experimented to see what could happen if herbivores—including different grasshoppers from middle elevations—inhabitant in alpine meadows at advanced elevations and came across new plant communities there. The study was issued recently in the Science journal.
Different grasshopper species were translocated from middle altitudes (1,400 m above sea level) to three alpine grassland sites at elevations of 1800, 2070, and 2270 m above sea level, where the grasshoppers were kept in cages. The researchers detached local grasshoppers from the investigational areas before the experiment, which was performed in the Anzeindaz region in the Vaud Alps.
As part of the study, the team restrained how the biomass, structure, and composition of the alpine plant communities diverse under the impact of the herbivorous insects. They also investigated whether certain plant species were more exposed to herbivory, for example, plants with harder leaves, or those that contain more silica or other components like tannins or phenols.
Lowland Grasshoppers Influence Alpine Community
The ecologists found that the feeding activities of the grasshoppers had a clear impact on the flora structure and conformation of the alpine flora. Alpine communities show clear structure in the organization of the canopy, where plants with tough leaves are at the top and more shade-tolerant plants with softer leaves are at the bottom.
However, there was an impact on this natural organization since the translocated grasshoppers tended to feed on taller and tough alpine plants, which had functional characteristics like leaf structure, chemical defence, nutrient content, or growth form analogous to those of their previous, lower-elevation food plants.
Thus, the insects reduced the biomass of dominant, tough alpine plants, thereby supporting the growth of smaller plant species evaded by the herbivores. This led to a growth in the total plant diversity in the short term.
“Immigrant herbivores consume specific plants in their new location and this changes and reorganises the competitive interaction between those alpine plant species.”
Patrice Descombes, Study First Author, ETH Zürich
Global warming, for example, could distress the ecological balance since mobile animals, such as the different species of herbivorous insects, can extend their habitat to higher elevations more quickly associated to sedentary plants.
Thus, herbivorous insects from lower altitudes could simply make their way into alpine habitats where resident plants are ineffectively or entirely not ready to protect themselves against the new herbivores.
This could change the current structure and purpose of alpine plant communities as a whole. Thus, climate change would have an unintended effect on ecosystems, apart from the direct consequences of increasing temperatures.
Important Drivers of Changed Ecosystems
According to Loïc Pellisier, Professor of Landscape Ecology at ETH Zürich and WSL, this indirect impact of climate change on ecosystems is one of the most crucial results to be obtained from the study.
“Climate impact research has largely investigated the direct effects of temperature on ecosystems, but these novel interactions that arise between species moving into new habitats could generate important structural modifications. They are important drivers of changed ecosystems in an increasingly warm climate.”
Loïc Pellisier, Professor of Landscape Ecology, ETH Zürich
Using the study outcomes, the researchers aim to improve models that have fallen short of completely contributing such processes until now. Moreover, they hope that this will increase the prognosis of how climate change will affect the functioning of ecosystems and the services they offer.
Descombes, P., et al. (2020) Novel trophic interactions under climate change promote alpine plant coexistence. Science. doi.org/10.1126/science.abd7015.
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