Planting trees in your yard is one way you can help combat climate change. Carl D. Walsh/Staff Photographer

The climate is changing, becoming hotter overall and more extreme. No person who spends time outdoors can argue with that. People with a let-business-do-whatever-it-wants philosophy can argue about what is causing the change (although some 97 percent of scientists agree it is likely caused by human activities), but they can’t reasonably argue that it is not changing.

So far, local farmers and home gardeners have not made huge changes in the way they farm and garden in order to ensure that plants thrive despite climate change, nor to slow the progress of this impending disaster.

“The things you are going to want to do are mostly good things to do even if weather wasn’t changing,” said Glen Koehler, a scientist specializing in pest management and fruit trees for the University of Maine Cooperative Extension. “The need for these good-farming practices just becomes more intense.”

Good, healthy soil is a top priority. Ivan J. Fernandez, a soil scientist professor at the University of Maine who also works with the school’s Climate Change Institute, said the key is to make sure soil has lots of organic matter – for several reasons.

“More organic matter in the soil means that there is less carbon in the atmosphere,” Fernandez said, and atmospheric carbon is a major contributor to warming temperatures.

In addition, carbon in the soil holds water, meaning plants will be less affected by long periods without rain. Soils with little carbon become hard on the surface, so much of the rain that does fall runs off rather than soaking into the soil. That runoff also causes erosion.

Resistance to erosion and ability to hold onto water are especially important, because climate change will mean (already does mean, many would argue) that rainfall is coming more often in heavy downpours, followed by longer dry spells.

So how do you keep organic matter in the soil?

Winter cover crops, which I wrote about Aug. 11, add organic matter as well as prevent erosion.

Experts also advise gardeners not to bag up and throw away organic matter such as kitchen compost, fall leaves, garden pruning and lawn clippings. Instead, add them to lawns, compost bins and gardens. Many people also recommend no-till methods of growing as better at keeping organic matter in the soil.

Beyond the soil, experts also suggest that farmers and gardeners expand the variety of the plants they grow.

“By using a diversity of crops and a diversity of planting times, you can take advantage of the variations in the weather that are going to come,” said Ellen Mallory, an Extension educator based at Orono. With frosts coming later in the fall, growers can extend their seasons, she said.

Matthew Wallhead, an ornamental horticulture specialist with the extension, said that he has noticed that garden centers are selling more plants that previously would have been considered too tender for the nursery’s locale. “The industry is definitely doing it,” he said, “and homeowners could try it on their own if they want.”

He cautions that problems could occur because of the winter cold; although global warming means the average temperature is warmer, extreme lows still can occur. For that reason, gardeners who try to extend Maine’s growing zones may want to give such plants extra wind protection.

Elsewhere, some professional gardeners are experimenting with assisted migration, the subject of a talk given by Smith College biology Prof. Jesse Bellemare at Coastal Maine Botanical Gardens last year. Here’s how it works: Some plants are disappearing from their native areas because temperatures are getting too warm for them. In nature, plants spread in part when wind or animals move seeds, but that spread may not be able to keep up with the pace of climate change. Assisted migration involves horticulturists digging up and moving threatened plants.

The concept has two potential problems, Bellemare said in his talk. One is that horticulturists would move only the plants they deem attractive. Next, once moved, the plants could become invasive in their new sites. More invasive plants is another overall threat of climate change, as warming temperatures make it easier for invasive plants to spread and outcompete desirable species in an area.

Wallhead noted that avocados have been deemed invasive in some parts of the country. And Bellemare discussed in his talk an umbrella magnolia planted at Emily Dickinson’s home during the poet’s lifetime that is just now seeding itself in the nearby woods. Before the recent warmer temperatures, the umbrella magnolia could survive in Massachusetts, but it could not reproduce.

Improving soil and expanding plant diversity in your own garden is a good start, but more can be done to combat climate change. For one, plant trees. Big trees. Big trees hold a lot of carbon. While growing a few oaks in a suburban lot in Maine won’t counteract the fires in the Amazon rainforest, every little bit helps.

Also, “gardeners’ biggest impact on carbon dioxide emissions is burning of fossil fuels,” Mallory said, “so if they can reduce fossil fuels in the garden and greenhouse, it would be a big help.”

Cut down your use of gasoline-guzzling mowers, rototillers, leaf blowers and other machines that also destroy the peaceful quiet in neighborhoods.

Wallhead agreed, adding that if growers limit what they bring onto their property, such as compost, and limit what they send off it, such as autumn leaves, it will have some impact in slowing the earth’s problems. A lot of gasoline is burned moving around those products.

Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at: tomatwell@me.com