Extinction of a Species is Compensated by Remaining Ecosystem

By Patrick Yang ’20

Figure 1. Biodiversity loss is partially compensated by the altered behaviors of remaining organisms.

Figure 1. Biodiversity loss is partially compensated by the altered behaviors of remaining organisms.

Biodiversity loss is often associated with ecosystem degradation because it is assumed that a species’ ecological role vanishes along with the species in the case of extinction. Current models of ecosystems utilize this assumption and predict an accelerated decline in ecological properties as biodiversity loss increases. Although this is a logical prediction, Dr. Martin Solan at the University of Southampton and fellow researchers have considered that there are compensatory responses produced by the remaining species after a non-random extinction. In other words, in the event of biodiversity loss, remaining organisms will alter their behavior to compensate for the vacant role left by the extinct species. This being said, current ecological models do not account for these population dynamics and may be inaccurate.

In the recent study, Dr. Solan and his team focused on the effects of biodiversity loss in marine invertebrates on sediment bioturbation, or the mixing of sediment by organisms. Although the mixing of seafloor sand does not seem very impactful in large ecosystems, bioturbation returns oxygen and nutrients to the water, which consequently promotes the growth of organisms. Dr. Solan’s team collected field data of 139 invertebrate species from Inner Galway Bay in Ireland over an 11-month period that each conduct bioturbation. Each species’ bioturbation potential was gauged using measurements of body size, abundance, activity level, and method of sediment mixing.

Using the field data as parameters, numerical simulations were created to model alternative extinction scenarios and sediment mixing depths to determine the effect of biodiversity loss on bioturbation. In consideration of potential compensatory responses, separate simulations modeled sediment mixing depth after potential responses from each species. These compensatory responses include, but are not limited to, behavioral and physiological adjustments, elevated growth, and increased reproduction. Extinction scenarios and nuances in the type and strength of the compensatory response were considered in the study, resulting in scenarios of partial, complete, or over-compensation. With the additional factor of compensatory response, these simulations diverged from previous models.

As a result of this experiment, future models will also include compensatory responses when considering biodiversity loss. The creation of a more sophisticated and representative ecological model can allow scientists to properly direct their efforts in the conservation of habitats.

 

References:

  1. M.S. Thomsen, et al., Consequences of biodiversity loss diverge from expectation due to post-extinction compensatory responses. Scientific Reports 7, (2017). doi:10.1038/srep43695.
  2. Image retrieved from: http://safari-and-marine-ecosystems.wikispaces.com/Picture+Gallery?responseToken=0192027fe4ef4ab586d5684f3c8be6d2c.
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