Keeping their cool: desert plants have a lot to teach us about climate change adaptation

Climate change isn’t new. The earth’s organisms have faced the “cope, adapt, or die” paradigm presented by changing climatic conditions since the inception of life on earth more than 3 billion years ago. Some species already live in extreme conditions (a topic demonstrated in the last blog post) – at the earth’s freezing poles in the dead of winter, at the apex of tropical mountain peaks that receive tens of meters of rainfall a year, and deep in the dry deserts that comprise a third of  the earth’s land area.

The plants and animals able to survive these extreme conditions may have something to teach us humans about climate change adaptation—especially when the organisms are incapable of crawling up to a cooler elevation or slithering into a deeper riverine pool to escape a heat wave. As a general rule, plants spend their lives rooted to a single spot on the earth. So they need to be able to withstand 365 days per year of whatever nature can dish out in terms of weather. Plants from hot deserts—such as the prickly cholla cactus—are no exception, and they have evolved a broad range of impressive strategies for coping with the hottest, driest climate in North America, where a years’ worth of rainfall may come in a single extreme event.

Optuntia sp. blooming in the Mojave Desert (copyright Sophie Parker 2008)

These desert denizens provide us with valuable insight into biological and physical adaptations that allow for survival on a hotter, drier planet that is subject to extreme events (as climate change experts are currently forecasting). In addition, deserts plants hold fascinating keys to longevity: the California deserts are home to both the world’s oldest tree—a Great Basin bristlecone pine (Pinus longaeva) between 5,062 and 5,063 years old—and “King Clone”, the oldest clonal colony of creosote bush (Larrea tridentata), which is estimated to be 11,700 years of age. From the perspective of climate change and adaptation, the ancient creosote clone is particularly intriguing, as the climate under which it originally germinated (at the tail end of the last ice age) was different from that in which it lives today.

What strategies allow desert plants to survive harsh conditions? Well, plants protect themselves from intense heat by producing smaller leaves (spines in cactus), by using water-saving methods of photosynthesis (such as Crassulacean acid metabolism), by growing protective hairs to deflect sunlight, or by producing thin leaves that cool down easily in a breeze or waxy leaves that prevent water loss. They can also capture moisture by having short roots that expand when it rains, or extremely long, fast-growing roots that can quickly tap into groundwater. Cacti contain flexible structures that allow their stems to expand and store extra water to use when it isn’t raining. Finally, plants have evolved the ability to delay germination and growth to coincide with water availability and mild temperatures, thereby avoiding the exposure of tender young seedlings to the harshest conditions.

You may be thinking at this point: these adaptations are great, but why should I care? Beyond their intrinsic beauty and their support of other desert species, plants have tangible benefits to offer society. Using biomimicry, scientists and engineers have begun to copy the strategies of animals and plants in nature in order to solve human problems. Desert plants may serve as particularly helpful guides as we attempt to adapt to a hotter and drier planet. We’ll have the best chance to learn from them if we protect the habitats where they are found.