What is the Key to Stable Ecosystems? Researchers Find Answers in Economic Principles

In order to get a stable return on investment and mitigate overall financial risk, an economic portfolio should be diversified, meaning that individual assets should vary with distinct characteristics. This long-standing principle is widely used in the world of finance —but how might it apply to other areas, such as the environment?

The key to a stable —and therefore more resilient— ecosystem is also diversification. Think of species as the assets for which you want to minimize risk. Species with different characteristics, such as growth cycles or response to environmental conditions happening at asynchronous times, lead to an overall stable ecosystem by ensuring that critical ecological functions can always be carried out. While this kind of diversity-stability relationship has been studied for decades, researchers now wonder how changing environments and the threat of invasive species are affecting ecosystem functioning and stability.

This idea and more were recently addressed in a study from the Department of Integrative Biology led by PhD student Reilly O’Connor and Dr. Kevin McCann. The study looked across both space and time at the changing density of different zooplankton species in Lake Simcoe to determine its impact on overall ecosystem stability.  

Zooplankton were an ideal choice for the study due to their integral role in aquatic food webs and biology. They consume phytoplankton while also serving as important prey for other ecologically significant species, with the added bonus of having a short life cycle. “Zooplankton have fast turnover times. They can allow us to look at what happens within their populations during a single season and see how the changing seasonality of climate might influence the species’ dynamics,” says O’Connor.

In the study, zooplankton density was measured across both time (1986–1999 and 2008–2019) and space (different communities and locations in the lake). The historical data came from long-term monitoring programs led by the Ontario Ministry of the Environment, Conservation, and Parks.

O’Connor and McCann adapted a framework commonly used in fisheries management to help them understand how ecosystem stability, synchrony, and diversity work together to influence stability from an ecological standpoint —and made a number of key findings in the process.

One finding was that seasonal asynchrony of different zooplankton species in local communities had the most stabilizing effect during seasonal changes in the environment, and seasonal species asynchrony was positively correlated with species diversity.

But they also found significant downward trends in ecosystem stability over a longer time frame —specifically, between the 1990’s and the 2010’s. With species diversity decreasing and synchrony increasing over this period, researchers are left worried.

Local and global environmental changes around Lake Simcoe, like warming temperatures, shifting ice conditions, and multiple invasive species, could explain these observations. However, more work on this topic is needed.

The next step to build upon the study’s findings would be to link the relationships between stability, synchrony, and diversity within a certain ecosystem to specific environmental changes, such as the addition of invasive species, or worsening climate change.

The study contributes to a growing body of science that is trying to uncover the best way to measure synchrony across a wide range of ecosystems, so researchers can better understand how organisms will respond to climate change. “These frameworks on synchrony, diversity, and stability are relatively new, and there's more work that needs to be done on extending this to freshwater ecosystems,” says O’Connor.

Just as economic theory has contributed to sound financial investment advice for many people, ecologists like O’Connor and McCann hope that these same principles may be able to advance the science of global change —in this case, with a return on investment that can benefit all.

Read the full study in the journal Ecological Society of America.

Read about other CBS Research Highlights.