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How will climate change affect native plants?

Maryland temperatures are predicted to increase 5⁰ F to 11⁰ F by 2100. Higher temperatures will cause native plants to experience more heat-related stress, a situation that will be made worse by longer droughts. Warmer temperatures will cause earlier leaf out and bloom times, de-synchronizing relationships between plants and their pollinators. Invasive plants will become even more aggressive because higher atmospheric carbon dioxide (CO2) levels preferentially promote the growth of invasive plants.

Graph from NOAAs Maryland Climate Summary

Some species will adapt to the changing climate, allowing them to maintain or even expand their natural ranges. Native species that still thrive in your region, for example, have adapted to all the climate change that has occurred so far. City native plants have also adapted to all the warming associated with the urban heat island effect, and they have done so in just a few decades.

This common milkweed is thriving in a Washington D.C. hellstrip. This species’ ability to conquer the urban heat island suggests it can tolerate some climate warming. In fact, herbarium studies show that common milkweed is expanding its natural range southward despite climate change.

As the climate warms, the temperature conditions with which a species co-evolved will move north or to higher elevations. But plants can’t just get up and migrate the way some animals do. Plants migrate through seed dispersal. For northward migration to work there must be large, contiguous blocks of natural area. Species that are adapted to life on Maryland mountaintops are in peril because there are no higher elevations to migrate to.

Plants in tidal habitats must also cope with sea level rise. As of 2018, around the Chesapeake Bay, sea level is rising at a rate of ¾”to 1” every 5 years. Additionally, tidal environments are being pounded by more intense storms. Unfortunately, upslope migration is often blocked by hardened shorelines.

There are several things you can do to make your native garden plants more resilient to climate change. For example, don’t plant natives in conditions that are too sunny or too dry for them, and avoid species that are near the southern end of their natural range. Gardeners can also help protect wild native plants by helping to preserve natural area corridors that species need for migration. You can get more detail on these topics by visiting our Native Plants and Climate Change webpage.

Trees are different from other types of native plants because they live longer. If you buy a tree now, you need to select one that will be adapted to temperatures in the year 2100. In a best-case scenario (society begins to curb climate emissions now, left), the arrows point to where Marylanders should currently source native trees from.  In a worst-case scenario (we do not change our emissions behavior), the red arrows (right) indicate where you should source native trees. These maps also show about how quickly plants would need to migrate. Could they migrate from Virginia to Maryland by the end of the century? Seems possible. From Georgia to Maryland? Less likely.

By Sara Tangren, Ph. D., Senior Agent Associate, Sustainable Horticulture and Native Plants, University of Maryland Extension, Home & Garden Information Center (HGIC)

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