We are in an extraordinary moment. Awareness of the risks facing our planet is growing and people are leaning forward, looking for a hopeful solution. On Half-Earth Day, October 23, thought leaders from around the world are gathering to showcase model conservation efforts, research, exploration and discovery that are working to achieve the goal of Half-Earth and protect our planet.
Why must we save half the Earth? Two lethal crises in the global environment have arisen under the human regime. The first is climate change, which is reversible. The second crisis, which in contrast is not reversible, is the worldwide extinction of species and natural ecosystems. This spread of death is removing Earth’s billion-year-old environmental support system. If not halted, and even if climate were to be stabilized, the losses will in time turn Earth from a metaphorical to a literal spaceship. The first steps in technology are already on the table. A few scientists are exploring the possibilities of geoengineering, including the release of particles and chemicals into the sea and atmosphere in order to counteract climate change. As biodiversity is stripped away and replaced by artifacts the world will be run less by nature and more by human terranauts.
Terranauts is a rare term, occasionally used in fantasies. As the name implies, it will be in reality the scientists and engineers who fly the planet like an oversized space vehicle. They and their robots will spin the dials and click the keys to provide our food, potable water, and the very air we breathe. At some point humanity no longer will be able to rely on the life-giving resources granted by nature.
What we call nature, the living natural environment, consists of three levels of biological organization. At the top are ecosystems such as pastures, woodlands, and coral reefs. In the center are the species that compose each of the ecosystems in turn. Finally, at the foundation are the genes, which prescribe the traits that distinguish the species that compose the ecosystem.
Every species, every kind of antelope, conifer, orchid, algae, butterfly, spider, and roundworm, constitutes a population of organisms that freely interbreed with one another while remaining reproductively isolated from all others. How many species exist today on Earth? Since the Swedish naturalist Carl Linnaeus began censusing them in 1735, a bit over two million have been identified and given a Latinized scientific name. How many species actually exist? When algae, fungi, and insects with other invertebrate animals are added to the vertebrates (birds, mammals, reptiles, amphibians, fishes), the best estimate is about ten million. Sampling and statistical analysis estimate that eighty percent of these species remain undefined. Any experienced naturalist can tell you: we live on a little known planet.
How fast are these surviving species going extinct due to human activity? Answer from the fossil record: somewhere between 100 and 1,000 times faster than before the spread of humanity, and the rate is accelerating. If this trend continues, we could wipe out most species by the end of the century.
So how can we fix the problem? The solution consists of two parallel tracks. The first is called Half-Earth. If half the surface of the land and half the surface of the sea are managed to conserve biodiversity, we can protect 85% or more of Earth’s species, including ourselves. This approach, conceiving conservation as an explicit overall goal, as opposed to a process, has become a lodestar, engaging the public and convening the conservation community to achieve this solution.
The second, parallel solution, a long-term adjunct of Half-Earth, is to create a Linnaean renaissance of understanding about species and their interactions within ecosystems. A renaissance of taxonomic research would accelerate the effort to discover, describe, and conduct natural history studies for every one of the 8 million living species estimated to exist, but still unknown to science. This reinvigorated research, added to that on known species, will contribute immense amounts of information to both conservation and general biology, allowing us to effectively manage protected habitats.
The challenge - all-in, full global conservation - is formidable, but worth the effort, given the magnitude of the reward for humanity and for all generations to come. We can do it, and why not? Scientists and the general public already think it appropriate to map and collect some 100 million nerve cells in the human brain. At much less cost, we ought to be able to find and map the 10 million species believed to exist, for no less a goal than to save Earth’s living environment. Half-Earth Day will be the first step in showing the way.
Edward O. Wilson is a prominent conservation biologist and Pulitzer Prize-winning author who is often called the "heir to Charles Darwin." He is a professor at Harvard and lecturer at Duke. Learn more about the E.O. Wilson Biodiversity Foundation.