Could Climate Change and Habitat Destruction led to an increase in Species Diversity?

By: Megan Nelson

As the rate of climate change and habitat destruction increases, a better method in determining a species’ survival becomes more important. With better models, scientists would better be able to predict which species are at risk of extinction and have a better chance of protecting them. However, determining an appropriate model that encompasses the many variables in nature is difficult. For instance, the effects of habitat destruction compared to the rate of climate change, which occur simultaneously, all the while comparing the evolutionary traits present in a species is extremely difficult. Nevertheless, each variable should be given consideration in order to better understand the survival rate of a species.

In a recent study led by Francisca Soares dos Santos, a simulation was used to determine the survival rate of four “species” based on habitat destruction, the rate of climate change, and four trade-offs that compared colonizing abilities to competitive abilities. The paper was published online as of September 2010 as a part of the Ecological Modelling Journal, and is scheduled to be published in the November 24 2010 issue.

The study began by using four different traits thought to span the general abilities of organisms in an ecosystem. The traits were placed in two different categories: colonizing ability, which consisted of the average dispersal distance (such as seeds in plants) and the production rate of seeds; the second category was the competitive ability, consisting of adult mortality rate and the competitive strength of seeds (for instance, by how much they weigh). These traits, arranged into four different trade-offs, dealt with colonizing versus competition: average dispersal distance vs. adult mortality rate, average dispersal distance vs. the competitive strength of seeds, seed production rate vs. adult mortality rate, and seed production rate vs. competitive strength of seeds.

The four “species” used to demonstrate the effects of the trade-offs, rate of climate change, and habitat destruction were arranged based on the ability to colonize: best, good, poor, and poorest. All four “species” underwent a different trade-off, and within each trade-off, was subjected to 70% indirect (such as change in food abundance) and 70% direct (such as a forest wipeout) habitat destruction. In each scenario (i.e. four “species”, one trade-off, and one type of habitat destruction), the rate of climate change was observed at relatively low and high rates. In addition, each scenario was compared to the result of no habitat destruction.

The study focused on the rate of decline, or increase, of the “species” in each scenario to determine which ones would survive in certain environmental stresses. In each scenario, habitat destruction lowered the diversity of “species”, but the amount by which it lowered was dependant on the trade-off. Regardless of the type of habitat destruction, an increase in climate change appeared to increase diversity in the average dispersal distance trade-offs compared to the rate of seed production trade-offs.

For the average dispersal distance trade-offs in indirect habitat destruction, the good and poor colonizer “species” were able to survive relatively low rates of climate change. For direct habitat destruction, the poor and poorest colonizers, or the best competitors, were able to survive the same amount of climate change. In the trade-off of seed production rate vs. adult mortality rate at low levels of climate change, for both indirect and direct habitat destruction, all “species” tend to survive, although at lower amounts. For low levels of climate change, and in both types of habitat destruction, for the seed production rate vs. competitive strength of seeds trade-off, the best and good colonizers tend to survive. In high levels of climate change, for both types of habitat destruction, only the best and good colonizers survived or only the best colonizer survived, depending on the trade-off. Overall, the diversity in both indirect and direct habitat destruction decreased for low levels of climate change. For high levels of climate change, there were three possible outcomes in the overall change in diversity. For the trade-offs of the average dispersal distance, in both habitat destructions, the maximum diversity is at the intermediate level of habitat destruction. For the trade-off of seed production rate vs. adult mortality rate, the diversity level was zero because only one type of “species” survived. Finally, for the trade-off of seed production rate vs. competitive strength of seeds, also in both habitat destructions, the diversity decreased with increasing habitat destruction. Overall, the best, good, and poor colonizers have the best chance of surviving habitat destruction, depending on the type of trade-off, and the rate of climate change.

This study appears to answer the problem of determining a model that predicts the survival of species given many variables. The model and methods that were used (i.e. the trade-offs) showed that traits must be taken into account in order to understand the combined effects of habitat destruction and climate change. For example, scientists must observed a species’ trait to colonize poorly to properly determine its survival based on habitat and climate changes. Using this knowledge of combined effects becomes very relevant in understanding and predicting the response of species and ecosystems to both climate and land change.

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Reference

Soares dos Santos, F., Johst, K., Huth, A., and Grimm, V. (2010, November). Interacting effects of habitat destruction and changing disturbance rates on biodiversity: Who is going to survive? Ecological Modelling, 221 (23), 2776-2783. doi: 10.1016/j.ecolmodel.2010.08.005