In 1901, the Atlantic cod, the staple of fish and chips everywhere, could be found off the coast of Canada weighing 60 pounds. In recent years, they average 18.6 pounds, a 69 percent reduction. The fish had evolved.
The evolution is a response to human-induced pressures on the population, according to a paper by incoming UC Santa Cruz professor Eric Palkovacs.
Palkovacs’ paper, “The Overfishing Debate: an Eco-Evolutionary Perspective,” discusses how people are unknowingly causing the evolution of different characteristics, or traits, in wild populations. But these changes are not limited to cod — they’re happening everywhere.
“[The] range of human effects that can cause contemporary evolution is quite large, and ecological consequences can be quite widespread,” Palkovacs said. “By changing the traits of species, people can be changing the way ecosystems work.”
Currently at Duke University in North Carolina, Palkovacs will be a faculty member at UCSC in July. Palkovacs’ research focuses on fish and fisheries, systems which he said are dramatically affected by human-induced evolution.
Stephan Munch, a fisheries ecologist for the National Oceanic and Atmospheric Association (NOAA), explained why fisheries are so affected by humans.
“In harvesting wild populations, we selectively kill the animals with traits we value, so these traits decrease in frequency,” Munch said. “We tend to harvest larger fish preferentially to smaller fish. This results in populations that mature earlier and at smaller sizes, which tend to produce fewer offspring.”
Palkovacs said these changes can also affect the diet of the fish, wreaking havoc on local food webs.
“When fish are smaller, sometimes the prey they consume changes because they no longer reach a large enough body size to consume some of the larger prey items,” Palkovacs said.
In fact, as Palkovacs and colleagues detail in another paper, “Fates Beyond Traits: Ecological Consequences of Human-Induced Trait Change,” these changes are not even limited to fish. Species everywhere are evolving in response to human pressures.
Climate change, pollution, dam building and trophy hunting are just a few of the issues that are causing species to change rapidly. In their paper, Palkovacs and colleagues report that evolution caused by people can occur two or three times faster than natural evolution.
“[One] major aspect of this area of research that is really an important point to emphasize is the speed at which these evolutionary changes are happening,” Palkovacs said.
These trait changes are widespread and caused by many factors, which could make overcoming them very difficult. Pearse, an evolutionary biologist working with NOAA, says different species require different techniques to mitigate these problems.
“It depends a lot on the life history and biology of the species that we’re looking at,” Pearse said. “It’s going to be really different for different species.”
However, Palkovacs said not all of these trait changes need to be mitigated. Despite the extensive research that has been conducted on the damaging effects of human-induced change, he said there are a few circumstances in which it has actually had a positive effect on the environment.
Species can respond to human effects by evolving greater resistance to environmental change, Palkovacs said. This actually helps buffer the entire ecosystem against future impacts. Research on these positive effects is rare, however Palkovacs said that might be because of how hard the effects are to study.
“[That’s] a very difficult process to actually study because your evidence becomes the absence of change, and it’s very hard to study the absence of change,” Palkovacs said.
Human-induced evolution will continue to be the focus of Palkovacs’ work when he begins at UCSC, which he said he is very excited about.
“It provides the ideal environment for me to explore my research interests,” Palkovacs said. “My major research objectives will be to continue to explore these linkages between contemporary evolutionary processes and ecological processes.”
