Climate change and invasive species
This complex relationship is notable because climate change and invasive species are also considered by the USDA to be two of the top four causes of global biodiversity loss.
[6][7] The destabilization of climate factors in these ecosystems can lead to the creation of a more hospitable habitat for invasive species, thus allowing them to spread beyond their original geographic boundaries.
Measurably warmer or colder conditions create opportunities for non-native terrestrial and marine organisms to migrate to new zones and compete with established native species in the same habitat.
However, most literature focuses on temperature only and due to the complex nature of both climate change and invasive species, outcomes are difficult to predict.
Considering the changing dynamics mentioned above, Hellmann et al. (2008),[4] concludes that invasive species should be defined as "those taxa that have been introduced recently" and exert a "substantial negative impact on native biota, economic values, or human health."
Consequently, a native species gaining a larger range with a changing climate is not considered to be invasive, as long as it does not cause considerable damage.
Invasive alien species are also capable of reducing the resilience of natural habitats, and agricultural as well as urban areas, to climate change.
However, most literature focuses on temperature only and due to the complex nature of both climate change and invasive species, outcomes are difficult to predict.
Climate change will interact with many existing stressors that affect the distribution, spread, abundance and impact of invasive species.
For instance, mechanical control of invasive species by cold, hard freezes or ice cover can become less effective with increasing temperatures.
[19] Several researchers found that climate change alters environmental conditions in a way that benefits species' distribution by enabling them to expand their ranges to areas where they were previously not able to survive or reproduce.
Climate change can cause increases in extreme weather like cold winters or storms, which can become problematic for the current invasive species.
[21] More extreme climatic events such as floods may also result in escapes of previously confined aquatic species and the removal of existing vegetation and creation of bare soil, which is then easier to colonize.
For example, despite an invasive species ability to reach these new environments, their presence could lead to disruptions in the food chain of that ecosystem potentially causing large scale death to others and themselves.
Invasive species typically have better tolerance to different environmental conditions increasing their survival rate when climate changes.
[26] Insect pests have always been viewed as a nuisance, most often for their damaging effects on agriculture, parasitism of livestock, and impacts on human health.
[27] Influenced heavily by climate change and invasions, they have recently been looked at as a significant threat to both biodiversity and ecosystem functionality.
[28] There are a plethora of factors that contribute to existing concerns regarding the spread of insect pests: all of which stem from increasing air temperatures.
The confused flour beetle population is expected to increase the most in higher latitudes [34] Areas with a warmer climate or lower altitudes are predicted to experience and decrease in crop pests.
While certain weather changes will affect species differently, increased air moisture plays a significant role in the rapid outbreaks of pathogens.
As these invaders move in, species endemic to the benthic zone will have to adjust and begin to compete for resources, destroying the existing ecosystem.
[38] The bull trout has a positive population growth or holds a competitive advantage only in streams that do not exceed 4–7 °C (39–45 °F) in the warmest months.
The geographical range of invasive alien species threaten to alter due to climate change, such as the brook trout (Salvelinus fontinalis).
To forecast future impact of climate change on distribution of invasive species, there is ongoing research in modelling.
[24] The models generally simulate current distributions of species together with predicted changes in climate to forecast future range shifts.
[57][58] Models have also investigated the impact of invasive species on local climate change--for example, accelerating the increase of wetlands as a result of the loss of forest canopy.
Additionally, climate variables that are directly linked to greenhouse emissions, such as alterations in temperature and precipitations, are likewise difficult to predict with certainty.
How species range shifts will react to changes in climate, e.g. temperature and precipitation, is therefore largely unknown and very complex to understand and predict.
Other factors that can limit range shifts, but models often do not consider, are for example presence of the right habitat for the invader species and if there are resources available.
[57] The level of accuracy is thus unknown for these models, but they can to some extent be used as indicators that highlight and identify future hotspots for invasions at a larger scale.
