​​Much of the theoretical research in the McCann Lab asks a deceptively simple question: What allows complex ecosystems to persist in a variable and changing world?

Our earlier theoretical work showed that ecological complexity need not be destabilizing. Rather, the organization of that complexity matters. Weak interactions, spatial heterogeneity, asynchronous dynamics, movement and flexible consumer behaviour can all stabilize food webs by preventing ecological dynamics from becoming concentrated into a small number of strong pathways.

More recently, we have begun to bring these ideas together under the broader concept of adaptive capacity. Natural ecosystems have evolved in environments that vary across space and time. As a result, organisms possess a range of responses—from rapid behavioural and physiological changes, through movement and demographic responses, to slower ecological and evolutionary change—that allow them to respond to this variation.

Importantly, these responses do not occur independently of the food web. When consumers move, switch prey, alter foraging behaviour or change their energetic demands, they change who interacts with whom and how strongly. In this sense, adaptive capacity at the organismal level becomes expressed as the dynamic structure of the food web.

Variation, Food-Web Structure and Resilience

A central idea emerging from our theoretical work is that variation itself can be a source of resilience.

Spatially heterogeneous landscapes provide organisms with alternative habitats, resources and pathways through which energy can move. Temporal variation similarly creates different opportunities through time. Mobile and behaviourally flexible consumers can respond to this variation, effectively tracking resources across landscapes and through time.

This produces what we think of as ecological portfolio effects. Just as a diversified financial portfolio spreads risk among investments, ecological systems can spread risk across populations, habitats, resources and trophic pathways. When conditions deteriorate in one place or along one energetic pathway, organisms may shift toward another.

The consequence is an ecosystem with multiple potential channels through which energy can flow.

Global Change and the Loss of Adaptive Capacity

This perspective also changes how we think about global environmental change.

Environmental change does not simply increase or decrease temperature, nutrients, productivity or habitat. It can also change the structure of environmental variation itself.

Human activities frequently homogenize landscapes, synchronize previously distinct habitats, remove species, simplify food webs or repeatedly favour the same ecological pathways. Even increases in productivity can ultimately reduce resilience if that production becomes concentrated into a single dominant channel.

From this perspective, ecosystems may become vulnerable not simply because environmental conditions have moved beyond some average threshold, but because the biological and spatial variation that once allowed organisms to respond has been eroded.

Our theoretical work therefore asks how global change alters the architecture of food webs and, ultimately, the adaptive capacity of whole ecosystems.

Trophic Hotspots and Spatial Food-Web Theory

An important extension of this work concerns trophic hotspots—localized areas of elevated productivity or resource concentration that attract mobile consumers and generate disproportionately strong trophic interactions.

Hotspots can arise from physical processes such as wind, currents, river mouths, thermal gradients and seiches, or from biological and geomorphic processes that concentrate resources. Consumers can then move among these productive patches, coupling otherwise distinct parts of the ecosystem.

Our theoretical work asks when these hotspots stabilize larger ecosystems, how consumer movement connects them, and what happens when landscapes are altered so that hotspots disappear, become inaccessible or become synchronized.

This provides a direct connection between classical food-web theory and landscape-scale ecosystem management.

From Food-Web Theory to Ecosystem Management

Ultimately, our theoretical research is increasingly concerned with identifying the structural properties of ecosystems that allow them to absorb environmental change.

This includes understanding interaction-strength distributions, weak interactions, consumer movement, spatial heterogeneity, portfolio effects, food-web rewiring and the distribution of energetic pathways across landscapes.

A major goal is to determine whether changes in these properties can provide structural early-warning signals of declining ecosystem resilience. Rather than waiting for populations or ecosystem functions to collapse, changes in food-web architecture may tell us that an ecosystem is losing the adaptive capacity that previously allowed it to respond to environmental variation.

In this way, our theoretical research moves from a longstanding question in ecology—what makes complex food webs stable?—toward an increasingly urgent one:

What features of ecological complexity must we maintain if ecosystems are to remain resilient in a rapidly changing world?

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