SUSSESSION

Change can be good! From the time life began on planet Earth, there have been many changes. The earth has had many eras with different dominant species. From the mass extinction of the dinosaurs to the building of massive cities, life finds a way to adapt to even the most dramatic changes. Primary succession is the way plants colonize and create soil from barren wastelands; secondary succession is how ecosystems adapt to small- and medium-size disturbances in their environment.

Small natural disturbances sometimes can actually create stronger and more resilient ecosystems. For example, a small- or medium-size wildfire will destroy a part of the forest. The burned area becomes a new microclimate for other smaller plants. New grasses, wildflowers, and bushes will grow over the area, creating new types of habitat. This allows for more biodiversity (a variety of wildlife) throughout the forest, which makes for a more resilient ecosystem. Some ecosystems have even evolved to depend on these kinds of intermediate disturbances, such as wildfires, floods, or seasonal frost.

Big or small, disturbances are inevitable for all ecosystems. Disturbances can be as small as a truck parked on a lawn, or as destructive as the volcanic Permian-Triassic extinction event, which killed over 70 percent of life on Earth about 250 million years ago. As far as we know, life has always bounced back from such disturbances—the only difference is how long it takes to recover. The greater the disturbance, the longer it takes for life to return. Sometimes recovery can take millions of years.

The expanding human population has been hard on our planet—the increase of pollution and the expansion of cities are transforming the earth in ways that are causing animal and plant species to go extinct at a rapid pace. Some scientists think that this human transformation of the land will be the next great extinction level event for many species. We share the planet with wildlife, and as humanity continues to build, we need to be conscious of the disturbances we impose on other species.

WASTELAND: A volcano erupts, a meteor hits, or land is paved over. Now there is a lifeless environment. Life can return quickly or it can take hundreds to millions of years.

PIONEER SPECIES: Weather like rain normalizes the land. The wind brings hearty bacteria and microscopic plants, and spores like those of lichen, moss, and algae. They live and die, and over time, soil begins to form.

FERTILE SOIL: Barren rocks are broken down by time, and the life cycle of these pioneer species begin to make fertile soil where small plants can begin to grow.