The history of the human race is littered with genocide and war. Each one is remembered and grieved by people throughout the world. Earth’s most recent genocide is happening at this very moment, and while most acknowledge it, few grieve it and even less are trying to stop it.
Human induced extinction events are causing the loss of species throughout the planet, but worst affected is our freshwater ecosystems. This issue was highlighted in a lecture with Michelle Jackson who has studied the pressures human activities are putting on these ecosystems. Freshwater ecosystems are the most vulnerable as they are usually at low points in the land and suffer from the collection of toxins, pollutants and invasive species from the wider environment. The accumulation of these “stressors” is impacting these fragile ecosystems in slaughtering fashion.
The loss of biodiversity in the freshwater environment is due to the accumulation of many different stressors into the ecosystem, the interaction of which causes many adverse effects. While stressors can occasionally negate each other, studies are showing that the majority of the time they are acting in synergy to harmfully affect freshwater ecosystems. Stressors in the marine environment are usually human introduced impacts such as toxins, metals, nutrients and invasive species.
A study by Jackson et al (2016) conducted a meta-analysis of 261 different studies to examine just how much these stressors are affecting our freshwater ecosystems. It was discovered that these stressors impact ecosystems in many ways, from the biodiversity to the functionality of the ecosystem. This study also found that that the presence of one stressor often increased ecosystem resilience to others. Jackson et al have speculated that this is due to the natural selection of adapted individuals who are tolerant to both stressors, reducing their impact on the wider ecosystem. Consequently It was observed that on occasion, a more tolerant species could compensate for the loss of another species and so while diversity dropped, functionality was stable. For this reason freshwater biodiversity loss is the main impact in the degeneration of freshwater ecosystems. While it was discovered that on occasion stressors could benefit ecosystems in novel ways, such as the addition of small amounts of nutrients, the study found that 86.22% of stressors impacted ecosystems negatively. 91.64% of these impacts affected insect and vertebrate communities in a detrimental and devastating way.
Freshwater warming was also found to work in synergy with stressors. In the marine environment warming is a stronger impact due to the thermos-separation among depth, it does not have as strong an effect in a freshwater ecosystem, but is still an impact, especially when paired with stressors. While warming was observed to help with the problem of acidification on phytoplankton populations and when paired with nutrients actually benefited some aspects of the system. It was observed that when in combination with contamination, warming had a significant antagonistic interaction on the ecosystem and resulted in many adverse effects and local extinctions.
Stressors are acting as evolutionary drivers toward tolerance but in order to stop the loss of biodiversity we need to effectively manage freshwater ecosystems in order to reduce their exposure to stressors and biodiversity loss. A key finding by Jackson is It has been shown in the past that these ecosystems can “come back from the brink”. This is a nice thought, but ultimately it may be futile as Jackson highlights that ecosystems are being driven towards degradation as the source of stressors continues to develop. Population growth, agricultural expansion and intensification, invasive species and industrial toxins are winning the war for the future of viable aquatic ecosystems. We can see the devastating effects of this war as extinction events are increasing and water quality is decreasing. In the developing world water is becoming so polluted that clean freshwater is now a product sold on the black market and rural suicide rates have skyrocketed as farmers cannot access this invaluable resource. Aquatic ecosystem stabilisation and restoration needs to be a target for the present, not the future. If we do not actively fight against invasions and stressors now, there might not be a future for these fragile, rare and important ecosystems.
