Dante Moroni 5/13/15 Final Exam

The way in which plants and animals respond to climate change is a sum of several interworking processes. In the past, climate change has been at a timescale slow enough for organisms to adjust, and the impact of humans on their environment had been significantly less. Now, this is not the case, as greenhouse gas emissions continue to rise along with the human population. The result is a climate which is changing at an unprecedented rate. In addition to worldwide urbanization and land use changes, this new environment may prove difficult for many species including ourselves, and depending on which representative concentration pathway plays out, 15-37% of species could be “committed to extinction” by 2050 (Thomas et al. 2004). Without addressing the impacts of rapid climate change, we could soon be facing the next great extinction.

In the past, species could migrate along with a slowly changing climate and had mechanisms which could keep pace to sustain robust populations. However, this is hardly true in modern times. Intensely fragmented landscapes resulting from anthropogenic causes, the most frequent being urbanization and mass agriculture, are making migration increasingly difficult for many species, especially those with limited dispersal abilities. Examples of how habitat fragmentation coupled with climate change is already affecting species can be seen in France, where limited dispersal in lowland plants will likely result in biotic attrition (Bertrand et al. 2011). Without the ability to migrate, organisms are forced to rely on their innate plastic responses in order to survive. This strategy has been successful in the context of inter-annual variability, though the magnitude of projected climate change is likely to push these plastic responses past their maximum range.

Being unable to migrate or survive through plasticity, many species have begun and will continue to experience intense selection. Historically, selection has led to those traits most suited for survival to become more common, aligning with a favorable environment. The evolutionary timescales of the past will not be relevant with rapid climate change, and mere selection may not be a sufficient evolutionary mechanism, especially due to the loss of genetic diversity in such a short time. However, rapid adaptive evolution has been show to be a potential solution for species, such as in wild Brassica rapa (Franks et al. 2007). Those species with short lifespans and high genetic diversity may benefit from the increased pressure, though the majority of species will suffer harsh reductions in fitness over the short term that may lead to extinction. Even though biodiversity is vast and the loss of a few species may not seem impactful, when the mutualistic relationships between them are taken into account, the whole ecosystem will suffer due to the loss of key species. Examples of this includes those plants specialized to be pollinated by a particular pollinator, or how coral reef ecosystems contribute a substantial portion of ocean biodiversity.

Just as these factors may seem to be an insurmountable barrier to retaining the health of biotic systems around the world, there are examples of success and potential to overcome adversity. Most of the outcome will depend on plants and animals surviving without human intervention, though we must take responsibility into our own hands in order to mitigate future

Dante Moroni 5/13/15 Final Exam

losses. Several techniques for preserving biodiversity and increasing the chances of species remaining extant will be valuable tools in the fight against climate change. These include seed saving programs which preserve genetic diversity for future generations, creating corridors that will allow for migration of species across the landscape, and in specific circumstances assisted migrations (Hoegh-Guldberg et al. 2008). Also, policy makers will need to play a major role in issuing guidelines for conservation groups and agencies that are specific and layout an action plan, along with revising barriers to climate adaptation such as the endangered species act (Jantarasami et al. 2010). In conclusion, mitigation of climate change through reducing greenhouse gas emissions along with intervention techniques to help organisms respond accordingly are necessary in order to reduce the loss of biodiversity and to retain the health of our own environment and that of the biota which surrounds us.

Sources

Bertrand, R., Lenoir, J., Piedallu, C., Riofrio-Dillon, G., Ruffray, P., Vidal, C., Pierrat, J-C., Gegout, J-C. 2011. Changes in plant community composition lag behind climate warming in lowland forests. Nature. 479: 517-520.

Franks, S.J., Sim, S., Weis, A.E. 2007. Rapid evolution of flowering time by an annual plant in response to a climate fluctuation. PNAS. 104: 1278-1282.

Jantarasami, L.C., Lawler, J.J., Thomas, C.W. 2010. Institutional barriers to climate change adaptation in U.S. national parks and forests. Ecology and Society. 15(4): 33.

Hoegh-Guldberg, O., Hughes, L., McIntyre, S., Lindenmayer, D.B., Parmesan, C., Possingham, H.P., Thomas, C.D. 2008. Assisted colonization and rapid climate change. Science. 321: 345-346.

Thomas, C.D., Cameron, A., Green, R.E., Bakkenes, M., Beaumont, L.J., Collingham, Y.C., Erasmus, B.F.N, Siqueira, M.F., Grainger, A., Hannah, L., Hughes, L., Huntley, B., Jaarsveld, A.S., Midgley, G.F., Miles, L., Ortega-Huerta, M.A., Peterson, A.T., Phillips, O.L., Williams, S.E. 2004. Extinction risk from climate change. Nature. 427: 145-148.