Tuesday, June 11, 2013

Invasive Species and Climate Change: How changing ecosystems will promote invasive species

Global climate change, spurred by excessive greenhouse gas production, is changing the way species interact with each other.  Due to changes in global temperature and precipitation patterns, ecosystems are changing, which is having a huge effect on individual species.  Many species will be forced to migrate to newer, more acceptable climates and will become invasive to their new habitats.  Invasive species, or exotic species that compete or exploit native organisms, can drastically change the composition of the ecosystems they are introduced in and have been known to cause species extinctions and change local environments, but they have also had some positive effects, such the introduction of the European Honey Bee to North America.  Invasive species often change the way ecosystems function by introducing new diseases, out competing native organisms, etc., and the consequences exotic species pose often have a great threat to humans by altering agriculture and destroying natural landscapes. We must further our learning of invasive species, especially in the current state of increasing climate change, in order to understand the potential impacts foreign organisms have on human-nature activities.  This blog analyzes current themes of global climate change and relates the impact of changing habitats to the promotion of invasive species.

 We are currently in a tread of rising surface temperatures and changing precipitation patterns due to increased greenhouse gas emissions.  Greenhouse gases (GHGs), notably Carbon Dioxide, Methane, water vapor, fluorinated gases and Nitrous Oxide, act as a blanket around the Earth, keeping in energy radiated off the Earth’s surface, as shown in the figure below (Greenhouse Effect).  Although there is much publicity about the negative effects of GHGs, they are naturally occurring and keep our planet warm, which is necessary for the lives of thousands of species.  But since the dawn of the Industrial Revolution, humans have been altering the composition of the atmosphere by releasing more GHGs than ever before through activities like fossil fuel burning, using inorganic chemicals, and applying nitrogen-based fertilizers to large-scale agriculture.  The increased concentration of GHGs has caused a period of rapid temperature increases and precipitation changes.  Because different ecosystems will be affected by climate change in different ways, some species will be able to adapt to the changing environment, while others will not.
Figure 1: The Greenhouse Effect

Invasive species may have an advantage over native species with the onset of global climate change due to their enhanced dispersal abilities.  According to Philip Hulme (2012), the dispersal rates of exotic species in both terrestrial and marine ecosystems are between 20 and 30 times as high as the maximum velocity of climate change.  This is significant because invasive species can redistribute their populations substantially faster than habitats will change.  Range expansions for plant and animal pathogens will also occur at unprecedented rates.  Approximately 65% of plant pathogens are invasive, and that number is very likely to grow with changing global climate because of changes in weather, water, temperature, and CO2 (Ziska et al. 2011).  Severe weather events, including hurricanes, may spread invasive pathogenic spores to agricultural areas through intense winds.  Increases in precipitation associated with climate change are likely to contribute to invasive pathogen germination and dispersal.  Warm temperatures are required for the growth of many pathogens; so global warming is likely to increase the geographical ranges for invasive pathogens.  Finally, because plants are dependent of availability of carbon dioxide for photosynthesis, higher atmospheric CO2 concentrations will likely increase plant-pathogen interactions.

Invasive species often lack predators in new environments, which promotes their success in new habitats.  Exotic organisms disrupt ecosystems by outcompeting other species and acting without environmental constraints.  Therefore, invasive species have a directly negative effect on biological diversity because they reduce the populations of native and endemic species and have even driven species to extinction.  According to NatureServe, invasive species “may compete directly with native species for food or space, may compete indirectly by changing the food web or physical environment, or may prey on or hybridize with native species” (Conservation Issues).  One example of the success of an invasive species in a new environmental is the overwhelming prosperity of the European Rabbit, or common rabbit, in Australia.  Introduced in 1859, the common rabbit experienced exponential growth due to its high fecundity and lack of predators, and their presence resulted in soil erosion and significant species loss (Gonzales 2011).  Figure 2 shows the distribution patterns of the European Rabbit in Australia in the late 1800s to early 1900s.  Although exotic species don’t always have negative consequences on native populations, a majority of case studies have demonstrated a negative correlation between invasive species and overall health of ecosystems.  Due to the complex interactions exotic species have with the ecosystems they are introduced in, it is difficult to predict the actual effects global climate change will have on invasive species distribution and overall biological diversity.
Figure 2: The Spread of the European Rabbit in Australia

 What can we do to reduce biodiversity loss as a result of the success of invasive species?  As global climate change causes ecosystems to greatly alter, plant and animal species will expand their natural ranges and will essentially become invasive at the extent of their new boundaries.  Because it will be extremely difficult to control the natural range expansion associated with climate change, we should focus on preventing the human caused distribution of invasive species.  The map below shows the distribution of invasive species around the world, and areas with the largest amounts of trade and urbanization are the places with the highest number of exotic organisms.  As demonstrated by Figure 3, the areas with the largest number of invasive species include some of the world’s largest trade centers, including Tokyo, Sydney, New York City, Seattle, and almost all of Western Europe.  Because the movement of natural resources often provides a means of invasive species dispersal, increased environmental regulations at ports will reduce the number of foreign species exposed through trade.

Increasing conservation efforts will help preserve biodiversity in the face of global change and will mitigate future challenges.  Conservation plans such as routine monitoring of easement lands, studying both macro and microhabitat, studying historical presence of invasive species, taking active policy measures to protect biodiversity, and restoring natural environments will help conserve biodiversity (Olmstead 2011).  Finally, increasing public awareness about the dangers exotic species pose on biodiversity is necessary to protect natural ecosystems.  As seen through the Ted conversation “Are you concerned about the spread of invasive species,” many people do not see the grave consequences that invasive species pose, so we must focus on reeducating the public about the dire need to control invasive species.

Figure 3: Global Map of Invasive Species Distribution


Works Cited

Are you concerned about the spread of invasive species? 2012. TED. http://www.ted.com/conversations/10062/are_you_concerned_about_the_sp.html

Conservation Issues. 2010. NatureServe. http://www.natureserve.org/consIssues/invasivespecies.jsp

Gonzales, R.T. 2011. “10 of the World’s Worse Invasive Species.” io9. http://io9.com/5833022/10-of-the-worlds-worst-invasive-species

Greenhouse Effect. 2013. National Geographic Education. http://education.nationalgeographic.com/education/encyclopedia/greenhouse-effect/?ar_a=1

Hulme, P.E. Invasive Species Unchecked by Climate. Science. 2012. 335:537-539.

Olmsted, J.L. The Butterfly Effect: Conservation Easements, Climate Change, and Invasive Species. Environmental Affairs. 2011. 38(1):41-76.

Ziska, L.H. et al. Invasive species and climate change: an agronomic perspective. Climate Change. 2011. 105:13-42.


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