Humans have an impact on the ecosystems in which they live — this is uncontroversial. However, the question of how exactly humans affect interactions within an ecosystem is still up for debate. New research by University of Calgary ecologists is shedding light on the scale of these impacts.
Dr. Tyler Muhly, who headed the study, described the focus of the research.
“The main thing we were looking at is how human activity on a large-scale landscape influences the distribution of various species that interact in a food chain,” said Muhly. “We wanted to see how human presence influenced where these species interacted on that landscape.”
The interactions between species and what shapes them has been the subject of much debate in the field of ecology, with the argument between a bottom-up or top-down approach.
“One of the ecological theories that we were testing was that predators have these effects on food chains from the top down. Predators regulate the species they eat, which in turn has an effect on the species that they eat, so it has a trickle down effect,” said Muhly.
Muhly and his team eventually discovered that the bottom-up effect seems to be what is regulating ecosystems in southern Alberta. However, the most groundbreaking findings were that this bottom up effect is principally a result of human impacts on the environment.
“People are having a bigger effect on plants in that system and as a result this is having an effect on the distribution of herbivore species, ultimately having an effect on predators,” said Muhly. “We really found that humans are a dominant species as far as influencing how food chains and food webs are regulated.”
Data for the study was collected over a period of five years through GPS collaring of animals, traffic counters and satellite imaging. The research was done in southwest Alberta, entirely outside of national parks.
According to Muhly, humans are influencing plants within the ecosystem by clearing forest in favour of grassland, planting crops such as hay, as well as adding chemicals to the system through the use of fertilizer.
As for the broader implications of the research, Muhly stressed the importance of remaining cognizant about the effects that human activity has on nature.
“If you’re trying to manage or understand how a given piece of the landscape works, you need to document what people are doing there,” said Mulhy. “You need to understand what people are doing and how that might affect the balance of food chains and food webs.”