In early August, the Intergovernmental Panel on Climate Change, a working group of the United Nations, released their latest report. The message was stark: human-induced climate change is ongoing at an unprecedented scale and, if not curtailed quickly, will have dire consequences. The implications of that assessment are far-reaching. But what might this mean for local parks?
First, a quick (very quick!) capsule summary of climate change. A fundamental element of ongoing climate change is a rise in global average temperature. On a planetary scale, the impacts of that warming are evident in phenomena like melting of polar and glacial ice and rising sea level. However, warming is not uniform across the globe, and that variable warming generates shifts in patterns of wind, precipitation, and ocean currents. As a result, the local experience of climate change may well include warming, but an additional effect is increased climate variability, including more frequent extreme events like droughts, hot spells, and storms.
The biggest driver of climate change is the greenhouse effect. Like the glass in a greenhouse, Earth’s atmosphere allows sunlight to pass through and heat the planet, but then blocks much of that heat from escaping back to space. Certain components of the atmosphere—known as greenhouse gases—are particularly effective at retaining heat. Carbon dioxide (CO2) is one of those greenhouse gases. Since the industrial revolution, human activity like burning fossil fuels has released huge amounts of CO2 into the atmosphere. At the same time, clearing of forests has reduced the capacity for plants to soak up that gas (which is what happens in photosynthesis). As a result, atmospheric CO2 levels have increased substantially, by 25% just since 1980, resulting in a warmer planet.
The most obvious consequences of that warming for local parks and natural areas would be direct impacts of previously inexperienced weather events, like spells of hot, dry, or wet weather. In Australia, die-offs of birds and mammals from heat stress have occurred already. Tolerance for variable climate, and the ability to escape unfavorable conditions, varies among species. The Audubon Society identifies 19 Ohio bird species (wood thrushes, scarlet tanagers, and others) that are “highly vulnerable” to climate change. Even a “moderately vulnerable” species like the tree swallow, a lovely summer resident of local parks, may disappear from some or all of Ohio as temperatures warm.
Changing climate can influence organisms’ life cycles in other ways, too. Many plants emerge and flower in association with warming temperatures. Studies of Ohio flowers reveal that with warmer spring temperatures, the date at which many flowers first bloom or reach peak blooming is earlier now than it used to be. For many insects, winter is spent in a dormant state (diapause), often in juvenile form (e.g., as caterpillars or grubs), supported by stored body fat. With warmer winters, the insects’ metabolism is increased so that they use their fat reserves more quickly. They may then be less able to fuel spring emergence and transition to the next life stage.
While changes to climate may create less habitable environment for some species, it also may create conditions that favor previously absent species. For example, the sachem skipper, a small butterfly, has limited tolerance for cold but has expanded its range northward as winters have warmed. Likewise, sandhill cranes, which historically migrated south in winter, now commonly remain in the northern Midwest, including Ohio, throughout the year.
Predicted changes in climate – warmer, wetter springs followed by hotter, drier summers – are likely to create change for forests, too. Growing seasons will be longer and may well favor success of many local tree species (sycamore, silver maple, and others), but other species (basswood, beech) may be less tolerant. Moreover, conditions also may improve for disease-causing organisms, and the smaller number of days with frozen soil may increase risk for erosion and treefall.
One concern of land managers is that climate change will particularly favor invasive species, which already pose substantial challenges to our parks. These opportunistic invaders often are more tolerant of unique and variable conditions than specialized native species. Kudzu and Chinese privet are moving north!
As climate change leads to new combinations of species, ecological relationships between species also might be altered. If spring migration of birds is triggered by changes in daylength (which is predictable), but insect emergence depends on local temperatures (which are changing), then climate change can create mismatches between the birds’ northern arrival and their food supply. Other mismatches might occur between the timing of plant flowering and the availability of pollinating insects, or between animals and the plants they rely on for support. For example, the monarch butterflies that grace Ohio meadows in summer feed on milkweeds in Texas on their autumn southward migration to Mexico, and they lay eggs on milkweeds in Texas on their way back north in spring. Changes to milkweed availability in Texas at either season can, ultimately, affect the abundance of monarchs in Ohio. In 2021, for example, Texas was hit by a winter storm that froze much of the milkweed crop; the monarch population in Ohio has suffered as a result.
Only time will tell how these processes play out in the years ahead. Both the magnitude of impending climate change and the ecological consequences of that change are complex and difficult to predict with certainty. However, climate change poses a diverse set of risks for Ohio and the Midwest. Actions by individuals, businesses, and governments can help to minimize the progression of climate change and preserve the biological systems and diversity that we have inherited. In the meantime, our parks can help to remind us of the riches of that diversity, and of the value in acting to protect our natural heritage.
Article and photo contributed by Dr. David L. Goldstein, Emeritus Professor, Department of Biological Sciences, Wright State University.