Exploring Ecosystems Health: Effects of Increments of Biodiversity and Trophic Complexity on the Stability of a Simple Gaian Ecosystem Model

Resumo

The concept of ecosystem health is explored, deepening the analysis on the relationship between biodiversity and ecosystem stability, both as variables for health evaluation. Ecosystem stability is studied under a systemic approach in terms of resistance and resilience. According to some authors, when ecosystems´s models consider not only the effects of organisms on the environment but also feedbacks from the environment to the organisms, the interactions between biodiversity and ecosystem stability become positive or even synergic. To test this, the “Daisyworld” model is used to simulate the effects of diversity and trophic complexity increments on ecosystem stability. For this, the model was consecutively run with: 1st one species of daisy, 2nd two species of daisy, and 3rd two species of daisy and a herbivore. To study the stability of the system, three perturbations were introduced: 1st, 50% reduction on the daisy population, 2nd, 10% decrease on the solar radiation, and 3rd, 10% increase in the solar radiation regarding the initial value. From the execution of the model, it can be concluded that increments on biodiversity did result in more resistance but less resilience. Nevertheless, it is considered that the system becomes healthier, as its self-regulation is improved, and the total biomass (productivity) increased. However, increments in diversity or trophic complexity are themselves considered positive in evaluating the ecosystemic health.