Introduction The statistics are sobering, the conclusions inescapable. During the last century, the average surface temperature of our world rose about 1 degree, whether measured Fahrenheit or Celsius. During the same period, the concentration of carbon dioxide in the atmosphere -- largely the product of industry and the automobile, worsened by deforestation -- rose about 25 percent. This is the gas that produces the "greenhouse effect" which holds the sun''s heat within the atmosphere. In an article in the British magazine New Statesman, Mark Lynas estimated that in England global warming "is equivalent to your garden moving south by 20 meters (65 feet) every day." An overall rise in global temperature doesn''t necessarily mean that your own garden will be 1 degree warmer this summer than it was last summer, or even than it was 5 or 10 years ago. What it means is that the weather will be less predictable. In 2003, the World Meteorological Organization (WMO) announced that a record number of weather extremes worldwide show that climate change is under way.

In June 2003, in Geneva, where the WMO is based, Genevans had the hottest June they''ve had for at least the past 250 years. Spring of 1999 in the northeastern United States was the driest spring since weather records began. Snowdrifts are deeper, winds are stronger, floods more devastating, droughts more severe. Tornadoes are more frequent -- a record 562 tornadoes in the United States in May 2003, which beat the previous record by 163. The WMO stated, "New record extreme events occur every year somewhere in the globe, but in recent years, the number of such extremes has been increasing." Meanwhile, freshwater supplies are in crisis, not so much because of the changing climate as because of our increasing demands. Long-standing water reservoirs are shrinking. Where the Colorado River enters the Gulf of California, it is now a trickle instead of the wide river it used to be.

The Ogallala aquifer below the Great Plains is being utilized far faster than it can be replenished. So is the aquifer under Mexico City, causing buildings to sink. While the average American uses 100 gallons of water a day, more than a billion people worldwide do not have clean drinking water at all. Gardening in a New Climate It might seem that your backyard garden doesn''t have much to do with such enormous changes, but there are adjustments you can make in attitude and practice which will make your garden more weatherproof and will also help conserve energy and water, whether you garden in a desert or your dry spell lasts only a week. We can emulate the farmers in dry areas who are turning to drip or trickle irrigation, which uses one-third to two-thirds less water than sprinkler systems, while increasing yields. Demonstration gardens utilizing low-water techniques are springing up across the continent in places like Montecito, California; Tempe, Arizona; Dallas, Texas; Greene County, Missouri; Stone Ridge, New York; Victoria, British Columbia; Wallingford, Connecticut; and Wichita, Kansas. Drought A garden designed to withstand drought can withstand other climatic extremes as well. What is drought? What is dryland gardening? David Phillips writes in The Climates of Canada (1990), "There are no universally accepted definitions of drought.

Any extended dry weather that is worse than expected and that leads to measurable losses can correctly be called a drought." So when the corn doesn''t grow past knee-high because there''s been no rain for six weeks, that counts as drought, even though the spring weather was wet. In fact, climate change in North America has meant a slight rise in precipitation, but it tends to be concentrated in fall and winter. If it comes as a deluge in October, it''s not much help in July. And because days are longer and hotter in July and August, the soil dries out roughly twice as fast as it does in spring. Because dryland gardens depend upon well-drained soil, they are better able to withstand periodic heavy rains than gardens with heavy soil. On the other hand, there are desert or semidesert places where the year''s rainfall is measured in fractions of inches or millimeters, and scarce water is a fact of life. Mediterranean climates such as California and South Africa and parts of South America and Australia (zones 8-10) generally have moist winters and hot, dry summers.

Gardeners everywhere are looking to the plants native to these places (and to dry slopes and meadows worldwide) to find what will grow for them when the rains fail. The term xeriscaping -- from the Greek word for dry -- was coined in the Arizona desert, where water used for landscaping was reduced by half when gardeners and landscapers chose xeric -- drought-tolerant -- plants and used water-conserving methods. This book will outline the methods and some of the plants that have been found most successful in gardens -- or even parts of gardens -- where the soil is dry for days, weeks or months at a time. It concentrates on zones 4 through 7, although some of the listed plants will grow in places warmer or colder than that. Using the techniques in this book and growing these plants, you will not only have a garden better able to survive extreme weather but a garden that conserves water and is easier to mind and manage. Cacti and Succulents Whether in the wild or in the garden, cacti and succulents are the plants best adapted to drought and least tolerant of wet ground. Cacti are native to the Earth''s western hemisphere, so they were unknown in Europe and Asia before Europeans arrived in America and took some of them back to Europe. There, these odd plants were given the Greek name kaktos, meaning cardoon or thistle.

In his Herbal of 1597, John Gerard described "Thistle of Peru": "It doth much resemble a fig in shape and bignesse, but so full of sharpe and venomous prickles, that whosoever had one of them in his throat, doubtlesse it would send him packing either to heaven or to hell." Cacti are supremely adapted to drought. The stem -- the body of the cactus -- is enlarged to hold water. It shrinks and withers after prolonged dry periods or in overly wet ground but stretches out full, like a balloon, when the plant is again content. Flowering happens soon after the rainy season. The leaves are mere thorns or hairs that do not lose precious water and, at the same time, help shade and protect the stem. The skin is leathery or waxy, the sap thick or milky. The root system is usually fibrous and shallow to take advantage of rainfall over as wide an area as possible.

All cacti have unique structures called aureoles on their stems and branches. The aureole has two buds: the lower usually makes spines; the upper produces new branches or flowers. There are a few species, especially of the genus Opuntia (page 119) that are hardy to temperatures as low as minus 40 degrees F (-40 degC). These are among the favorite cacti for gardens everywhere, but for desert or semidesert gardens, there are hundreds of species and cultivars that can create a beautiful and varied landscape. Succulents -- plants with fleshy stems and leaves, not spines -- are more adaptable in the garden than cacti, but they also do best where the soil is mostly dry. In desert gardens and arid rock gardens, cacti and succulents dominate. In wetter places, succulents such as sedum can be used quite freely in well-drained soil, but cacti are perhaps best treated as conversation pieces. Keep them away from passing hands and feet and from competition from grasses or plants that might shade them.

One of the best ways to show off cacti is in a small area of sand or gritty soil in a rock garden or traditional stone trough or in a large container with drainage holes. Pots should be at least 2 feet (60 cm) wide to accommodate the plants. Purchase special cactus mix, which is available in garden stores, or mix your own soil with 20 to 50 percent sand. Be sure to keep the pot.