Nature's Survivalists: How Plants Conquer Harsh Environments

Long before people invented extreme sports and reality shows to survive in adverse conditions, plants have been adapting to extreme habitats and growing conditions. From scorching deserts to windswept mountain peaks, these natural survivalists have developed strategies to withstand environments that would defeat most living things. Some endure centuries of drought by hoarding every drop of water, while others disguise themselves as rocks to avoid being eaten. A few even defy time itself, living thousands of years in barren soils with little more than sunlight and grit. This article explores four remarkable species that not only survive but thrive where few others can.

Monkey Puzzle Tree (Araucaria araucana)

Due to the monkey puzzle tree's lifespan, 1000 or more years, and skeletal frame with scale-like leaves, it has been called a "living fossil."  Further reinforcing this, 200-million-year-old fossils of a plant resembling the tree have been found. The evergreen, coniferous monkey puzzle tree is the hardiest species of its genus, native to the Andes Mountain volcanic hillsides along the coasts of southern Chile and western Argentina. Here, there are temperate forests with mild, cool climates.

But to maintain stability in the porous volcanic soils, the trees have extensive shallow root systems. The roots spread wider than the tree is tall, which can reach heights between 130 and 160 feet and has a 7–8-foot-diameter trunk. This, in turn, allows the roots to gather water and nutrients, as well as the tree to withstand strong winds. The thick, fissured bark, which resembles polygonal armor, helps make the tree highly fire-resistant. The tree has adapted its terminal buds and cones to be fire-resilient and its seeds (each cone has approximately 200) to quickly germinate in shaded fire-scarred areas. The monkey puzzle tree has additional regeneration strategies to add to its adaptation toolbox. If the terminal part of the tree is damaged, shoots will grow from the stump, and, with an extensive root system, suckers will colonize the area around the trunk. Culturally significant to the Araucarian indigenous people, its seeds (piñones) have been an important food source, but now the monkey puzzle tree is endangered due to illegal logging and habitat loss.

Bristlecone Pine (Pinus aristata and P. longaeva)

The bristlecone pine is another species that has adapted to mountainous terrain and is one of the oldest living trees in the world. Two species are found in North America: Colorado bristlecone pine (P. aristata) and Great Basin bristlecone pine (P. longaeva). Both species live in subalpine and alpine habitats up to an elevation of 11,700 feet. There are several survival strategies that the pine has in order to live on harsh slopes, through brutal winters, and during short growing seasons. The bristlecone pines have dense trunks, between 3 and 15 feet in diameter, and tend to be twisted from growing in high winds. Both species are low-growing compared to other pines. P. aristata averages 15–20 feet in height, but will grow up to 45 feet tall, whereas P. longaeva will only grow to 3 feet in height at the highest elevations.

The soil that bristlecone pines grow in is called dolomite, a limestone substrate, which contains few nutrients. In these areas, precipitation is limited, and temperatures are colder. Therefore, the root system is shallow and branching, covering a wide area to collect nutrients and moisture during the short growing season. A few thick roots are formed to maintain structural support, and as a tree gets older and taller, these roots may buttress, forming larger, wider roots to further support the tree trunk.

American Century Plant (Agave americana)

The American century plant is native to Mexico and the southwest United States. Home gardeners in this region and other hot, arid climates utilize agave species for their drought resilience and low-maintenance characteristics. The American century plant is highlighted as a specimen plant in "desert" areas of botanical gardens and conservatories across the country due to its unique bloom time.

True to its common name, the century plant blooms once in its lifetime, though it does not take 100 years. The mechanism that initiates bloom is still unknown, but the average lifespan is typically 10–25 years, though some plants have bloomed at 50 years of age. The flowering stalk, reminiscent of asparagus, can reach heights of 30 feet. The greenish-yellow flowers bloom on branched clusters (panicles) and attract a variety of insects. After flowering, the parent plant dies back, having produced multiple offspring, called pups.

Another adaptation in many agave species is a specialized mode of photosynthesis called crassulacean acid metabolism (CAM). While most plants in moist climates absorb and store carbon dioxide through microscopic openings on their leaves, called stomata, during the day, plants in arid climates do not. Instead, agave species, including the American century plant, reduce evaporation by opening their stomata at night. Plants that utilize CAM are being studied for climate-adaptive agriculture to introduce water-saving traits into bioenergy and food crops.

Living Stones (Lithops spp.)

Lithops are small succulents that survive in the arid habitats of South Africa, along with other members of the ice plant family (Aizoaceae). They have two kidney-shaped leaves, 0.5–1 inches tall and 1–3 inches wide. Despite their tiny size, lithops are power-packed survivalists. The leaves store water, allowing survival for months without rain, as desert areas receive less than 20 inches annually.

The name lithops means "stone-like," as the colors and patterns of the fused leaves mimic the sandy hills and stony ridges where the plant lives. The camouflage and small size allow the plant to escape predation. Living in a hot, arid climate, lithops ensure that their energy is well spent. A living stone will flower in autumn and early winter, and then the seeds will be formed. The capsules that house the seeds will only open when there is sufficient moisture in the area. They remain closed when it is too dry. This strategy allows the seeds to find a suitable place in the soil to root and gather nutrients.

Once the flowers die back and seeds are expelled, the plant enters a state of dormancy. Then, in the spring, new leaves form by absorbing the nutrients and moisture from the old leaves. With myriad adaptive strategies, this seemingly unassuming, tiny plant epitomizes a survivalist’s way of life.