Plants that once flourished are no longer thriving. Yet nothing has changed about the way you cultivate them. So what's going on and why?

Scientific studies confirm it

Several recent studies have shown that for every two degrees Celsius the climate warms, about 5% of Earth's landmass moves into a different climate zone. Scientific models indicate the pace of change is even faster for the next two degrees of warming, resulting in an additional 10% of land area shifting to a new zone. These changes are real and could mean you will need to rethink some of your gardening practices.

temperature change map

The root cause of the problem is human

Man-made emissions are changing Earth's atmosphere. Receding Arctic ice has made headlines for years because of the dramatic amount of melting that's occurring. Ocean levels are rising and obliterating coastlines. Animals, plants, and diseases are on the move as their territory shrinks and they're forced to seek new habitats.

Maps are having to be redrawn. For instance, the tropics become 30 miles wider every decade. Near the 100th Meridian, North America's dry Western Plains meet the wetter eastern region . Since 1980, this climate boundary has shifted approximately 100 miles to the east.

factories spewing steam and pollution

Half of all life Is on the move

For some time, scientists have assumed species would shift their ranges along with the changing climate, but many had not expected it to happen so quickly.

A National Geographic study of more than 4,000 species around the world shows approximately half of them are now on the move. Terrestrial species are moving on average more than 10 miles per decade; while marine species are moving about 40 miles.

The 100th Meridian where the Great Plains begin is shifting

As early as the 1870s, scientist and explorer John Wesley Powell wrote about the glaring transition between North America's Western Plains and the wetter eastern region. "Passing from east to west across this belt a wonderful transformation is observed. A luxuriant growth of grass gives way to naked ground with the occasional cacti". The line between the two regions runs from Mexico to Manitoba, Canada, straight through North America's breadbasket. To the east, farmers primarily grow moisture-loving crops such as corn. To the west, drought-resistant wheat is the primary crop.

Microclimates

landscaped lawn with shade and sunshine

Most yards contain microclimates that occur where atmospheric conditions are different from those of the surrounding area. These differences are usually minor, but they can sometimes be sizeable. Microclimate may refer to an area as small as a few square feet or as large as many square miles.

How microclimates form

The two main characteristics of microclimates are temperature and humidity. A change in either of these conditions is due to numerous influences and frequently to a combination of them.

The type of soil found in an area can also affect microclimates. For example, heavy clay soil can act like pavement by moderating temperatures near the ground. However, if soil contains numerous air pockets, heat can be trapped underneath the topsoil. This results in a greater possibility of ground-level frost.

frost on a leaf

The effects on your hardiness zone

Are your annuals that should be finished blooming by September still blooming in late October? Are your vegetable plants putting out new growth weeks later than usual? If you’ve noticed these or similar changes, you’re not alone.

If you've been gardening for several decades, you've probably noticed changes in growth patterns between then and now. Even though the planet is definitely getting warmer, changes in USDA plant hardiness measurements are officially being attributed to things like more accurate temperature measurements as well as taking into account proximity to bodies of water, elevation, and other microclimate effects.

However, just because zone 6b has been relabeled as 7a doesn’t always mean a particular plant will grow well in the newly-designated warmer location.

girl with a basket of vegetables

In some areas, climatic changes have been more gradual. In others, you can’t help but notice them. And they are affecting planting times, bloom periods, as well as ways gardeners may need to make adjustments in dealing with weeds and invasive plants.

Remember to always take into account the natural habitat of any plant you want to grow. For instance, some plants naturally thrive in hot weather, but may also require high humidity or a moist environment.

For some encouraging news about climate change click here.