What the humble clover means for the future of life in cities | Crosscut

Jennifer Vanderhoof, a senior ecologist with King County who monitors biodiversity and who wasn’t involved with this research, said the scale of the study is impressive. “The scope and breadth of sample locations, and the sample size are remarkable — as is the number of authors,” she said. Johnson said 126 of the co-authors were students.

But the study has limitations. The researchers evaluated the impacts of certain environmental conditions like snowpack and air temperature at single points in time, Vanderhoof said, rather than as trends or averages. 

Dr. Max Lambert, a senior scientist with the Washington State Department of Fish and Wildlife, who was not involved with the study, said that while it shows a pattern, it isn’t that consistent, which tempers how much can be concluded from the results.

“They have a similar pattern popping up in multiple places, but they have functionally two patterns — a positive and negative [gradient] — which is interesting. And they have most sites showing no pattern, which I think is also a very interesting pattern to me, but does complicate our understanding,” he said. 

Lambert noted that urbanization can mean more than one thing.

“It’s likely we’d find similar types of changes to be relatively common in many highly adaptable species, if we had the resources to look,” Vanderhoof said.

The management side

“Knowing that species are rapidly adapting to urbanization implies that in order to design resilient cities we need to take into account evolutionary change,” said Dr. Marina Alberti, a professor at the University of Washington who sampled with Dyson. Intentionally coaxing species to adapt poses important ethical questions, Alberti said, adding that we have the responsibility to think about evolutionary impacts when making design and natural resource management decisions.

Approaches that boost biodiversity in one place may not work somewhere else.

“For all the … species whose ability to adapt to changing conditions cannot keep up with the speed with which our climate is changing, our best bet is the protection of not just singular habitats but rather of entire ecosystems and suites of ecosystems,” Vanderhoof said. 

Whether it’s a good or bad thing that clover can adapt in this way depends on your perspective.

“If you care about conservation, then adaptation to cities and how humans are influencing evolution is a pretty darn important thing, and maybe a positive thing when they can adapt. But you can also understand why it may have negative consequences,” Johnson said. 

If clover survives, so too may species that depend on them, like pollinators. But we don’t get to choose which species have this evolutionary edge, and some of them may be invasive species that unsettle ecosystems, like zebra mussels; or species we consider pests, like bedbugs. Insecticides worked on bedbugs — until one bedbug with a helpful mutation passed on that mutation to its offspring. Johnson compares this to the coronavirus evolving to evade our vaccines. 

Some species that we want to survive — rare or keystone species — might not adapt on their own in certain places. In that case, humans may need to introduce hardier individuals from other populations to give biodiversity a fighting chance. 

Ultimately, Lambert said, changing human behavior may be the safer path than hoping plants adapt to us on their own. 

Vanderhoof said biodiversity work is complicated by how interrelated species can be; something that helps one species might negatively impact others. And even with plenty of money and political will to put biodiversity measures into play in cities, management may still get down to the question: What should we protect?

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