Nearly 2 billion people already live in water-stressed regions, where subtle shifts in average annual temperatures could mean inadequate water supplies for people and the environment, according to the Intergovernmental Panel on Climate Change.
When water is scarce in sub-Saharan Africa, people spend hours searching for and collecting drinking water. When drought hits Nevada, people have to change the way they wash their cars and tend to their yards.
In urban areas of arid Texas, about 25 percent of treated water goes toward landscaping, according to experts at the Texas A&M Department of Horticultural Sciences.
Even small steps can make a difference, so when planting this spring and summer, consider using native species already adapted to the environment you live in. They will require little more than natural rainfall. You can also make soil improvements that help absorb and hold water, and use mulch to prevent water loss through evaporation. "Mulch is your greatest ally in drought conditions," according to Organic Gardening magazine editor Ethne Clarke.
But most importantly, avoid these thirsty varieties:
Tropical and exotic plants: Species such as hibiscus and banana, commonly used in landscaping, come from tropical regions that get a lot of rain. These plants tend to have fairly high water requirements.
"Foliage structure tells you a lot about water needs," said David Ellis, editor of The American Gardener, the magazine of the American Horticultural Society. Plants with large glossy dark leaves tend to absorb more heat and require a lot of water, and a larger leaf surface area equals greater water loss. If hydrating is a concern, stick with hairy, smaller, and lighter-colored or silvery leaves that retain water and diffuse light, such as lambs ear, rosemary, or lavender, Ellis advises.
Exotics in general will probably need more water than native species, Ellis adds. Try to avoid rapidly growing tropical plants with soft, pithy, and fleshy trunks--these are usually plants with large water contents. The banana tree, for example, is 90 percent water.
If you live in a drought-prone region, stick with plants from the arid southwest, parts of California, or the Mediterranean, such as the above-mentioned herbs or drought-tolerant succulents, like agave and yucca.
Annuals: Generally sighted all around town during summer, short-lived annual plants, such as impatiens, often need a lot of water. Many annuals have a shorter growing season with intense blooms, and a corresponding shallow root system. Plants that have time to grow extensive and deep roots will be able to tap water deep within the soil and live longer in drought-prone regions.
It may seem counterintuitive, says Ellis, since large plants take more water to establish, but once they have found their footing, these hardy species don't require as much watering, and can provide shade--and relief from the heat--for much of your garden.
A traditional lawn: Americans are moving away from the idea of the perfectly trimmed emerald green lawn, Ellis says. "I think people are starting to realize that if you have to put up warning flags [about pesticides], that contradicts the idea of something beautiful to play on."
Most grass and turf species are on the list of thirsty plants to avoid. If you are still attached to the American dream, and are facing water shortages, consider drought-tolerant varieties such as buffalograss, or consider replacing at least some of your lawn with a garden of native species that attract wildlife and pollinators.
The concept of xeriscaping--landscaping that reduces the need for supplemental water--has slowly become accepted, according to Ellis. "Instead of [being thought of as] an ugly barren landscape, it has become an interesting way to integrate interesting shapes and colors."
A number of cities in drier parts of the country fund programs that will help transform thirsty yards to ones that use natives and drought-resistant plants, according to Organic Gardening's Clarke.
Xeriscaping pioneer and famous landscape architect Steve Martino writes on his website: "The landscape profession wasn't interested and clients were absolutely not interested [in xeriscaping when he started decades ago]. Cities were not interested and nurseries were not interested. Most resistance is now gone. Ideas I struggled to promote are now mandated."