Across the Laurentian Great Lakes, resilience may depend less on having the greatest possible number of species than on preserving the ecological variation that allows species, habitats, and food webs to respond differently when trouble arrives. A new synthesis published in Frontiers in Ecology & the Environment argues that this hidden diversity acts like a natural shock absorber, helping ecosystems continue producing food, supporting wildlife, and delivering essential services even as climate change, habitat destruction, invasive species, and overexploitation intensify.
The study, led by researchers at the University of Guelph’s Centre for Ecosystem Management and conducted with scientists from the Department of Fisheries and Oceans, Cornell University, the Great Lakes Fishery Commission, and the Ontario Ministry of Natural Resources, examines how ecological structure can stabilize ecosystems. Its central concept is the “portfolio effect,” a phenomenon in which variation among species, populations, habitats, and ecological functions reduces fluctuations in the system as a whole. The idea resembles a diversified financial portfolio: when investments do not all rise and fall together, losses in one area can be offset by stability or gains elsewhere.
In nature, this buffering begins with differences among habitats. A lake, river basin, or coastal landscape is not affected uniformly by a heat wave, drought, pollution event, disease outbreak, or invasive species. Shallow and deep waters may experience different temperatures; wetlands may retain water after surrounding soils dry; sheltered bays may provide refuge when open-water conditions become hostile. Because disturbances rarely strike every location with equal intensity, relatively intact areas can continue functioning and help sustain populations in more damaged places.
The same principle operates within biological communities. Different populations of a species may respond differently to temperature, food availability, predators, or disease. Species that perform similar ecological roles may also have contrasting environmental tolerances. If one declines during an extreme event, another may maintain the function it shared with the affected species. This does not mean that biodiversity makes ecosystems invulnerable. Instead, it lowers the probability that a single disturbance will disrupt every component responsible for an important process, such as nutrient cycling, carbon storage, primary production, or the growth of fish populations.
The researchers describe these stabilizing effects as operating across nested levels of ecological organization. Variation among habitats can support variation among populations; differences among species can preserve alternative feeding strategies; and multiple energy pathways can keep material and energy moving through a food web even when one route is weakened. Such interactions create what scientists call functional redundancy, although the species involved are not truly interchangeable. Each may contribute a unique combination of traits, timing, behavior, and relationships that becomes valuable under particular environmental conditions.
“Ecosystem resilience is not just about having many species, but about maintaining the variation within and across scales that helps the individual organisms, species, and ecosystems persist and adapt,” lead author Kayla Hale explains. The distinction is critical. A landscape can retain a respectable species count while losing the ecological differences that make those species respond independently. If habitats become nearly identical, populations are genetically and behaviorally narrowed, or food webs become dominated by a small number of generalists, the system may look diverse on paper but behave like a single vulnerable unit.
Human activity frequently pushes ecosystems in precisely this direction. Land transformation removes or fragments habitats, intensive harvesting can eliminate large or specialized organisms, and invasive species may homogenize communities by replacing locally adapted species with widespread competitors. Pollution and climate change can further synchronize ecological responses, causing many populations to experience the same stress at the same time. As this synchrony increases, the portfolio effect weakens: instead of compensating for one another, ecosystem components decline together, making the system less predictable and increasing the risk of abrupt ecological deterioration.
The Great Lakes provide a powerful setting for examining these dynamics because they combine enormous biological and economic importance with multiple interacting pressures. The basin supports fisheries, drinking-water supplies, transportation, recreation, and complex food webs extending from microscopic plankton to top predators. Changes in temperature, water quality, shoreline structure, nutrient availability, and species composition can ripple through these connections. The synthesis suggests that management focused on a single target species or isolated habitat may miss the broader structure that determines whether the whole system can absorb disturbance.
The authors therefore call for conservation and restoration strategies that protect ecological differences rather than simply maximizing averages. Maintaining a mosaic of habitats, preserving population variation, safeguarding species with distinct ecological roles, and protecting multiple energy pathways can give ecosystems more ways to respond when conditions change. This approach also favors management that avoids excessive synchronization—for example, by preventing the widespread conversion of varied shorelines into uniform developed landscapes or the concentration of resource extraction in ways that remove the same traits everywhere. In practical terms, resilience becomes a design goal: preserve enough variation that no single shock can disable the entire system.
The study’s broader message is that biodiversity functions as a form of natural insurance, but insurance only works when the underlying coverage is distributed across the system. Protecting rare species remains important, yet the research indicates that less conspicuous forms of variation—differences among habitats, local populations, ecological strategies, and food-web connections—may determine how ecosystems behave during the next unexpected crisis. In a rapidly changing world, conserving that layered structure could be one of the most effective ways to keep the Great Lakes productive, adaptable, and capable of supporting both wildlife and human communities for generations.
Subject of Research: Animals
Article Title: Managing for resilience with ecological structure: Portfolio effects in the Laurentian Great Lakes
Web References: https://doi.org/10.1002/fee.70057; http://www.ecosystemscience.ca
References: Hale, K.R., Fernandes, T.J., O’Connor, R.F., Ward, C.A., Cazelles, K., Bernhardt, J.R., Chu, C., Giacomini, H.C., Koeberle, A., Koops, M.A., Ludsin, S.A., Muir, A.M., Stewart, T., Tucker, C., Tunney, T.D. and McCann, K.S. (2026), “Managing for resilience with ecological structure: Portfolio effects in the Laurentian Great Lakes.” Frontiers in Ecology and the Environment, e70057. DOI: 10.1002/fee.70057
Image Credits: Centre for Ecosystem Management
Keywords: ecosystem resilience, biodiversity, portfolio effect, Great Lakes, habitat heterogeneity, ecological stability, climate change, invasive species, conservation, food webs
