Conservation refers to protecting ecosystems that have been relatively untouched by human development. Restoration means reducing or removing the types of modifications that humans have caused.
Let's unpack that a bit with an example:
Say 100 years ago we took two plots of land, identical to each other, and decided to perform an experiment. One was used for commercial development, someone built a house on it, lived in it for a while, planted a garden and a lawn, and then left the lot.
We decide to remove the house and garden and allow it to become "natural" once again. This plot would be considered a "restoration" project. But if we took the other plot and never developed it at all, we just allowed it to be, unaffected by people, for the full 100 years, this lot was "conserved."
Would you expect that the two lots would once again resemble each other? How long, if ever, would it take for the disturbed plot to match the one that was left untouched?
In truth, we can't estimate this without performing the experiment, but in all likelihood, the first plot would never be able to catch up. Why might this be the case?
A conserved plot of land has been allowed to go through its natural progression indefinitely, with no disruption to the cycles of nutrients, composition of microbes, and diversity of species. The other lot has essentially been reset after a 100 year pause, so not only does it have to catch up the 100 years that the untouched plot had, but it can never get back the entire history that it lost. In theory, these lots may have a similar ending stage where they settle and change relatively little (the climax community, see figure below), but the time it takes to reach it, or the likelihood of ever reaching it, is very different.
Succession is a principle in ecology where we can follow the path that an area takes in getting back to its natural state. Here we are focusing on man-made development and changes that were caused by people, but often succession is used to explore the way that areas respond to natural disasters or catastrophes such as wildfires, volcanic eruptions, or floods. Succession is categorized as either primary or secondary depending on how dramatic the disturbance was. If ALL life is wiped out and the area starts 100% from scratch, it is called primary succession. This is pretty uncommon. More likely, it will be secondary succession, where many of the species that make up the community are removed, but not all living things or nutrients are taken out of the environment.
In either case, there is an expected sequence of regeneration that the ecosystem goes through, and it occurs in predictable stages. As you might expect, species that take a long time to mature and take over the landscape are the last to recolonize the area. Quick growing species of plants or small, mobile animals would be among the first to come back. But tall trees and the species that rely on or live only in these forested areas might take some time to return.
Rewilding is a special case of restoration, and it can sometimes have nothing to do with buildings or development. Sometimes people can damage an environment in an indirect way. One of the best examples of rewilding in the United States is the reintroduction of wolves into Yellowstone National Park.
For much of the past century, hunters and farmers removed the wolf population that used to roam Yellowstone National Park and the nearby areas in Wyoming and Montana. By doing so, they disrupted the trophic cascade- removing the top predator affected their prey populations, the species affected by those prey, and the species affected by those species that are affected by those prey! Wolves here are considered a keystone species because their presence (or absence) can have a dramatic impact on the entire ecosystem.
Without wolves, the elk were free to stay in a favorite spot to nibble on the developing willow and aspen trees, preventing large trees from growing. After wolves were brought back to the park by biologists in 1995, they not only regulated the number of elk that were grazing, but they influenced the way that the elk behave. When wolves are around, the elk feel pressure to keep the herd moving, which varies their dietary preferences and allows them to provide nutrients and soil turnover in more widespread areas. As trees came back, so did beavers, building dams and changing the routes and environments of the streams and rivers. These dams formed pools for young fish to grow and develop, and the re-routed water allowed more growth in different areas than it had reached before.
Yellowstone was completely transformed after the wolves were brought back, and it is now closer to its pre-human state than it was 50 years ago. What would it look like if the wolves had never been removed? Did the decades without wolves have a permanent effect on the park?
It makes you wonder how different the land around you might look if it had never been disturbed, and I hope this inspires you to protect the undeveloped spaces that remain, or to set aside an area for natural wildlife to return and hopefully thrive.