Examining the makeup of a healthy ecosystem: Predators can help with climate resilience

I think ecosystems are really neat. The cumulative effects of multiple organisms just going about their lives and interacting with each other results in these complex, multi-dimensional webs of relationships that can have fascinating and unexpected results. Some of my enthusiasm is very much about aesthetic and entertainment. Diversity is the spice of life, and it just makes me happy knowing some of the weird shit that’s out there for no other reason than nothing stopped it from existing. The other big reason the topic fascinates me is that – as I repeat fairly often – we’re part of the global ecosystem, and play at least some role in every regional and local ecosystem. Our activities have touched every portion of the surface of this planet, and the results, while often horrific, have been fascinating.

It’s often hard to see exactly what role a given organism plays, but every once in a while, we’re able to do large-scale experiments, like re-introducing wolves to Yellowstone.

In 1995, Yellowstone brought the wolves back to the park. After 70 years without wolves, the reintroduction caused unanticipated change in Yellowstone’s ecosystem and even its physical geography. The process of change starting from the top of the food chain and flowing through to the bottom is called trophic cascades.  According to Yellowstone National Park, here are a few ways the wolves have reshaped the park:

Deer: It’s true that wolves kill deer, diminishing their population, but wolves also change the deer’s behavior. When threatened by wolves, deer don’t graze as much and move around more, aerating the soil.

Grass and Trees: As a result of the deer’s changed eating habits, the grassy valleys regenerated. Trees in the park grew to as much as five times their previous height in only six years!

Birds and Bears: These new and bigger trees provide a place for songbirds to live and grew berries for bears to eat. The healthier bear population then killed more elk, contributing to the cycle the wolves started.

Beavers and other animals: Trees and vegetation also allowed beaver populations to flourish. Their dam building habits provided habitats for muskrats, amphibians, ducks, fish, reptiles, and otters.

Mammals: Wolves also kill coyotes, thereby increasing the populations of rabbits and mice. This creates a larger food source for hawks, weasels, foxes, and badgers.

Scavengers: Ravens and bald eagles fed off of larger mammal’s kills.

Most surprisingly, the land: Soil erosion had caused much more variation in the path of the river. But with elk on the run and more vegetation growing next to rivers, the river banks stabilized. Now, the wolves have changed Yellowstone’s physical geography.

Unfortunately, I have a confession to make. In learning about ecosystems, I’ve mostly focused on ones where I don’t need special equipment to breath. I certainly learn about aquatic species, and about aspects of the aquatic “landscape”, both in oceans and in fresh water, but I don’t think I’ve really studied them as systems in their own right. Even when I was doing water quality and invertebrate analysis for a river near my high school, I wasn’t really thinking about it as a system, so much as a way to gauge pollution levels. Even so, it’s obvious that climate change is messing with our watery brethren just as much as life on land, and a research team from Trinity College Dublin and Hokkaido University have made an interesting discovery about how the presence of predators can influence the way heat waves affect life in streams:

The scientists assembled communities of freshwater organisms in experimental streams at the Tomakomai Experimental Forest in Northern Japan. The stream communities were exposed to realistic heatwaves, and some included a dominant predator (a sculpin fish), while others did not.

They found that heatwaves destabilised algal (plant) communities in the streams such that the differences normally found among them disappeared and they resembled each other much more closely—equating to a loss of biodiversity—but this only happened when the predator was absent from the community.

Algal communities are important in streams because they form the energy base for all other organisms, so loss of algal biodiversity can propagate to impact the entire ecosystem.

Additionally, the scientists discovered that important heatwave effects—such as shifts in total algal biomass—only emerged after the heatwave had passed, underlining that even catastrophic impacts may not be immediately obvious.

I keep saying that we need to start actively managing our ecosystems, to control how we affect them, as simply not affecting them seems to be both beyond our ability, and a denial of our nature as one organism among many. If we’re going to become the kind of stewards I’d like us to be, we will also need as great an understanding of our ecosystems as we can attain.

“Western” society has operated under the belief that the natural world exists for our convenience, and so it can be reshaped to suit our short-term interests. That led to extermination and genocide, and ultimately the total destabilization of our planet’s climate. That said, ecosystems are very resilient – we’ve been doing vast amounts of damage for generations, but while the scars from that area easy to see, life still, uh, finds a way.

Taking steps to stop adding to the harm is more than just a gesture of goodwill to the rest of the planet’s residents – simply making sure they’re able to go about their lives, in turn, makes it possible for us to do the same. In a lot of ways, it’s as simple as making sure you don’t eat everything in the forest, so that you know there will be more to eat next year.

If we take care of creatures like these grumpy-looking sculpin, they will help take care of us, without even trying.

Thank you for reading. If you find my work interesting, useful, or entertaining, please share it with others, and please consider joining the group of lovely people who support me at patreon.com/oceanoxia. Life costs money, alas, and owing to my immigration status in Ireland, this is likely to be my only form of income for the foreseeable future, so if you are able to help out, I’d greatly appreciate it. The beauty of crowdfunding is that even as little as $1 per month ends up helping a great deal if enough people do it. You’d be supporting both my nonfiction and my science fiction writing, and you’d get early access to the fiction.


  1. planter says

    While I agree with the general point that predators and other organisms higher on the food chain can be important in structuring many ecosystems, I would caution making too much of the Yellowstone example. The “wolves change rivers” meme has been driven by some very slick media productions that imply that this is a generally agreed fact. It is rather the case that there is a lot of debate among ecologists on the role that wolves are playing in this system. This paper is a very recent (and open access) contribution to the debate: Brice, E. M., E. J. Larsen, and D. R. MacNulty. 2022. Sampling bias exaggerates a textbook example of a trophic cascade. Ecology Letters 25:177-188. https://doi.org/10.1111/ele.13915

    Regardless of the role of top predators in any ecosystem, I think most if not all ecologists agree that they should be there, and that the ability to support a top predator population is a great indicator of an overall healthy ecosystem.

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