Invasive species - not human's fault?

Last week, I spoke about how humans have been responsible for the introduction of invasive species. On a second thought, there are other contributing factors to the spread of non-native species. Those factors indirectly push native species to their limits, and towards extinction. 

In 2011, EU raised concerns over threatened freshwater species. One of the major risks was alien species, they believed. However, there was little emphasis placed upon the direct introduction of these species by humans. Instead, invasive species, such as Chinese mitten crabs and Himalayan balsam were transferred through Europe's rivers. So, are humans not the source of trouble?

Reading into this - In fact, in the European coastal waters, 24.5% of non-indigenous species entered through the Suez canal. Only 9% of them was intentionally released. Occhipinti-Ambrogi laid out an important relationship between changes in the biosphere and development of invasive species. 

Stages in the development of an invasive non indigenous species. 

Note that the magnitude of the release of invasive species is greatly affected by climatic change. It interacts with non-indigenous species by altering the physical-chemical conditions (PCF) in relation to temperature and oceanographic characteristic. Then PCF contributes to the change of new communities patterns. As we are currently experiencing global warming, the warming of climate is a primary cause to physiological stress. This leads to mass mortalities in benthic organisms, especially those who were already near their tolerance limit. As a result, there will be empty niches for new colonisers (invasive species). 

Without getting distracted into the never-ending discussion of global warming, let's just focus on the complexity of invasive species and the route to extinction of native species. 

Certainly, non-native species play a critical role in driving native species out of where they were originated. From the previous blog, I mentioned how humans have intentionally introduced species to control another. However, the surge in invasive species very much depends on other factors too, such as global warming. But human activity is the main reason for rising CO2, hence the greenhouse effect?Although global warming can be blamed to have exacerbated the effect of invasive species, human is still the key underlying factor. 

Number of references found as evidence for each
mechanism and type of facilitation 

Despite all the negativities, some authors are determined to prove that invasive species do not only bring detrimental impact, like extinction. For instance, zebra mussels, as one of the invasive species, actually support up to 700% more taxa than neighbouring mussel-free habitat. Yellow perch also have higher growth rates as zebra mussel colonies provided increased availability of invertebrate prey. 

Turns out in certain circumstances, invasive species might actually have positive impacts on native species. 

Carry on from last blog, introduction of invasive species might not be entirely human's fault. Although it is one of the reasons behind the verge of extinction of many other species, on the other hand, it may actually have opposite effects, thereby facilitating positive interactions between no-native and native species. Not so hopeless after all?