Humans excel at classification. One of the wonderful tricks of neurocognition is finding similarities and patterns. Classification is the process by which things are differentiated so that similar things can immediately be recognized and with a basis of understanding established. Aristotle, the Greek philosopher and polymath, had some of the earliest definitive writing classifying and categorizing ecosystems and the organisms therein.
Today we often study "ecosystems" or "biomes" when trying to understand how plants, animals, weather and soil types all interact within a geographical location. These areas of interdependence are simplified by the predominant vegetation types therein. For example, certain types of leafy trees grow only if there is enough water and the temperature is correct—hence they are known as deciduous forest biomes. Other plant types colonize dry and arid climates, and their adaptations reflect where they succeed so we have "shrub land" or desert biomes. In either case, affinity for a certain climate allows certain plant types to dominate an area which creates a myriad of interconnected life with similar or complementary adaptations. The beauty is in the balance, the intricate interplays within each classification.
North America has several major biomes. In the northern reaches of the land mass, tundra is the dominant biome. Treeless tundra is a windswept world colonized by low-growing shrubs, grasses and lichens which do not require deep roots. Animals here travel far to take advantage of scant, ephemeral food sources. They are also well insulated to survive months of below-zero temperatures.
Geographically below the tundra is a forest of hardy conifer trees which are capable of sustained freezing temperatures and low levels of annual rainfall; this is often called the boreal forest. The spruces and pines here, and other plants their forest canopy allow, provide crucial food and shelter for many species of birds during breeding season. Some 325 different species of birds use the taiga forest as their nursery.
In a desert biome evaporation exceeds the amount of annual precipitation. This means plants and animals living in these particular areas have adaptations which allow them to conserve water. They are dominated by shrubs or succulents. The majority of North American deserts endure cold winters and hot summers, making them more conducive to shrubbery. Animals here have adaptations to extreme temperature changes and surviving long periods with no water.
Forested areas are either coniferous or deciduous biomes. The conifer forest dominates the western side of the continent. Here greenery persists year-round in the needle-like leaves of giant gymnosperms, or cone producing plants. In the eastern part of the continent swaths of color occur in trees like oak and maple that will lose their leaves yearly.
The middle of our continent was a prairie biome. In this area, species of large grasses were the most prevalent living thing. The soil in these regions were rich with biodiversity and organic material owing to grasses' fine clingy root masses that stabilized its moorings against erosion. In North America this region is the most agriculturally productive. Over the last 100 years the tall grasses have been replaced by agricultural grasses such as corn, and legumes like soybeans. Less than one-10th of 1% of the original prairie biome still exists.
Each of these biomes is usually defined by weather patterns and how plants and animals within a weather zone have been shaped to take advantage of various resources. Understanding this interplay is what we call ecology. At the heart of it all, each ecosystem or biome is a collaboration of working parts creating a system that is adapted to succeed and sustain.
Zooming out from any specific biome, there is ultimately just one: the Earth itself. That ecosystem/biome shares the same principles of any of the smaller classifications. It is a collective of working parts and those parts sustain each other in a myriad of ways.
April 22 has become a worldwide celebration and reaffirmation of the importance of this endlessly wonderous ecosystem we call Earth. From the initial "wake up" call to action in the early 1970s, Earth Day has brought people to work together and adapt for the greater good of the planet as a whole. This year's theme for Earth Day is Invest in the Planet.
Whatever you choose to do to celebrate Earth Day, let learning be a part of it. Learning the details of how a wetland or a forest fit together is inspiring beyond any words that can be written. A group of organisms that creates the tapestry of life is the result of innumerable trials all leading to a beautiful balance. Each mutation or adaptation is tested by the environment in which they must exist until settling into a pattern that works—which is the beauty of Earth. Happy Earth Day!