I’ve posted on synergies between environmental stressors (what most people think of as pollution) before. Basically, a synergy is when the impact of the two stressors, say increased CO2 nd nutrients, is greater than the sum of their individual impacts. Once you recognise that synergies can occur, and are often much worse than we predict, the next question is can we do anything to stop them? The short answer is in most cases yes.
The way that synergies work means that, theoretically, if you remove one of the stressors then the “extra” impact should also be removed. In essence, if a synergy is 1 + 1 = 5, then removing 1 means that 1 + 0 = 1. When you’re talking about impacts to ecosystems that are essential to our GDP and way of life (not to mention that they have intrinsic value anyway) that is a really big consideration.
One of my Ph.D. students has just published a rather elegant study demonstrating it is possible to disrupt a synergy between CO2 and nutrients that has the potential to cause the loss of our kelp forest ecosystems. Basically, where CO2 and nutrients cause the synergistic growth of “weedy” species of algae you can remove the nutrients and remove the synergy. There is, however, a caveat. If you wait to remove the nutrients from the system then a large part of the impact will remain – things won’t go back to normal.
The thing that I like most about this outcome is that it provides useful information to the people who manage our coastal waters. If you are concerned that increasing concentrations of CO2 will have a negative impact in areas around major population centres then recycling and redirecting treated waste water away from the ocean, such as into industry or agriculture, can increase the resilience of marine systems. But, timing matters. Sooner is better.