A study published by the journal Nature Communications shows that the actions of species that promote changes in the environment are important for the formation and maintenance of ecosystems, making them more stable. This is the case, for example, of elephants that deforest areas of vegetation or beavers that build dams in rivers with pieces of tree trunks. This is an innovative approach to the field of ecology, as it is more common for research to consider direct interactions between species rather than looking at the indirect effects that one species can have on others based on the changes they promote in the environment. in which they cohabit. The article was written with the participation of professors from Unicamp Mathias Pires, from the Institute of Biology (IB), and Marcus de Aguiar, from the "Gleb Wataghin" Institute of Physics (IFGW), as well as researchers from the United States, Canada and Germany.
Due to the immense variety of existing ecosystems, whose dynamics are marked by complexity, the researchers used mathematical models derived from physics for the study, based on the science of complex networks. This made it possible to focus the analyzes on the essential aspects of ecosystems, without taking into account variables that would be considered in an essentially biological approach.
"It's not just about representing species as numbers and quantifying them, we must also take into account the interactions that you consider fundamental to study the phenomenon you analyze. So you disregard several details, in Physics this is very common. Biology is complex, everything is important, everything influences. Still, some elements influence more than others. In our case, you have to think 'what am I interested in describing? What is actually fundamental to describing the phenomenon?' Then you reduce it to just those elements, disregard the details and see what happens", explains Marcus de Aguiar.
Another characteristic of the study is that it is not based on a real ecosystem, such as the Brazilian Atlantic forest or African savannas. The simulations are carried out based on existing knowledge and data on how interactions between species and the environment occur, but considering a space in the process of being configured by the dynamics of nature itself. In this way, researchers add species and interactions that prove to be essential and are able to measure the role and importance of each element.
"Ultimately, our model simulates what happens when a volcanic island appears, for example, where first there is clean land and then colonization by species occurs, a new ecosystem is created", explains Mathias Pires. The professor explains that in this process, ecological factors are analyzed, such as the number of levels of food chains formed, the number of possible interactions between species and how many of them actually occur, the degree of specialization of organisms, that is, whether they interact with just one another species or with several and, finally, the number of species possible to exist in the same space.
Therefore, the model developed by the researchers gives the freedom to design ecosystems with more or fewer species, with a greater or lesser degree of specialization and potential to interact with others. Depending on what the mathematical results indicate, they know whether the model is realistic or not. "What's cool about a theoretical work is that you can add and remove elements at will. You can check how important these elements are in the system. If I remove that, will it (the system) still be realistic? What's really important to reproduce what we observed?", reflects Marcus.
Contributions of engineering species
Based on the possibility of inserting different species into the dynamics of simulated ecosystems, the research reached a novelty that had previously been little explored by studies in the area: the data obtained through mathematical simulations indicate that species that interact with the natural space in which they live cause significant impacts on other species, favoring the establishment of new species in the same location and ensuring greater dynamics in these environments, making the ecosystem more stable.
"What we see is that the more of these species capable of modifying the environment you put in our model, the faster the acquisition of new species. It's as if they were actually shaping, reorganizing the environment, facilitating colonization by new species. If you have few of these species, there are many extinctions at the beginning", explains Mathias Pires. These effects of species called "ecosystem engineers" can be diverse. For example, the holes dug by armadillos in the ground are used by other animals looking for shelter. Another species of this type are bromeliads, whose leaves accumulate water where other types of organisms such as insects can develop. "What we show with the simulations is that these effects on the environment can shape how the ecosystem works. It is not something that is negligible", highlights the professor.
If, on the one hand, the indirect interactions provided by one species can benefit several others, its extinction can also result in a more intense chain of extinctions than can occur between species that establish a predator-prey relationship between them. Without the burrows dug by the armadillo, several species no longer have a safe place to breed and protect themselves from predators. "When a species goes extinct, it doesn't mean that only it died. If another species consumes it, it will also go extinct. So the extinction of a species can cause a cascade of extinctions. If you don't have these ecosystem engineers in model, these extinctions are more pronounced, the system is more unstable", reflects Marcus, drawing attention to the complexity that exists in these relationships.
Effects of humanity and evolution
The research that resulted in the article published in the journal Nature Communications integrates studies carried out by a working group linked to the National Institute for Mathematical and Biological Synthesis - NIMBioS, a research center based at the University of Tennessee, in the United States, which combines knowledge of biology and mathematics. With the development of the model, teachers evaluate the possibility of further research by adding other variables that have not yet been considered in the studies.
They highlight the potential of evaluating the interactions that can occur between different ecosystems, something that has not yet been considered by studies. Another possibility is to evaluate the effects of the evolution of species over time and how it relates to the interactions established between species and the environment, as well as the way in which these interactions can affect the course of evolution.
A third reflection stimulated by the research is that man's role as a species that engineers ecosystems can also be evaluated. In this way, researchers recognize how we are an animal species that modifies natural environments in a much more intense way compared to other species, which reveals the importance of investigating the complexity involved in ecosystems and using tools that make it more palpable. it's understandable. "The real world is much more complex than we can work with in mathematical models, but models are the tool to unravel this complexity", recognizes Mathias Pires.
The full article is available at Nature Communications magazine website.
