“A species is classified as endangered when its population has declined between 50 and 70%. This decline is measured over 10 years or three generations of the species, whichever is longer.”
– Red list of threatened species
Do we have any idea about what happens after an animal or plant species disappear? Worldwide, more than 27,000 species are endangered and close to extinction. This is equal to over 27% of all species known to humans.
There are two main reasons why species become endangered. Either they lose genetic variation or their habitat.
Extinction by Genetic Variation
The term genetic variation is used to describe the difference between same and different species. It’s what enables species to adapt when the environment changes.
In our case – human beings – genetic variation gives us different eye and skin colors, different height, different blood type, etc. If we have sex with a close family member and have children, those children will have little genetic variation. This type of offspring may have problems in the future. They become less resistant to diseases and cannot evolve when environmental variables arise. For this reason, populations with low genetic variation face a significant probability to become extinct.
When it comes to other species, loss of genetic variation can occur naturally (mutations) or be induced by humans. Think about overfishing, overhunting, pollution, the introduction of invasive species to the wild, and deforestation. These are all examples of the many human activities disturbing whole populations. Such disturbances force populations to become smaller and create fewer breeding mates. This leads to a poor genetic variation and then extinction.
Extinction by Loss of Habitat
When species disappear due to loss of habitat, that can occur by a natural cause. If the environment changes abruptly in a short period of time, several species may or may not be able to adapt to the new environment. This is what led dinosaurs to their extinction. Once again, extinction by loss of habitat is mainly caused by humans. While we grow cities, industry, and agriculture, millions of species get closer to the edge of extinction.
When humans make a whole species disappear, we play the role of natural selection. However, the way we do it is far from natural and seriously interferes with biodiversity. It interferes with the natural process of evolution that cannot keep up the pace of massive extinctions.
The Domino Effect
Think about the case of the gray wolf extermination in the U.S. during the 20th century. Gray wolves feed on deer, moose, and elk. They also control the population of beavers, raccoons, and coyotes. Without gray wolves, their prey populations grew exponentially. The massive growth of the elk population led to the depletion of willows and riparian plants. Consequently, the amount of food and shelter to songbirds decreased. This caused the growth of the mosquitoes population that were the food source of these birds.
Species like the wolf, rhino and polar bear are close to vanishing due to human activities. At the same time, a chain reaction or domino effect will create a conflict in the whole ecosystem — one species at a time.
The same happens with smaller species. Take the example of a tiny animal such as the mussel. While mussels filter water to get the nutrients they need, they also purify it. It’s what makes mussels such an essential piece in the aquatic ecosystem. Mussels serve as food to several other species, such as otters, ducks, baboons, and egrets. Without mussels, their predators have to move to a different area, with no certainty on finding other food sources.
Worldwide, bees are going extinct due to excessive use of pesticides, loss of habitat, and climate change. They are the bridge between plant reproduction, as they transfer pollen from the male stamens to the female pistils. Without bees, one-third of the global food supply will disappear. Since bees are a key to pollinate crops, no bees on Earth would immediately create a catastrophe. As Albert Einstein once said: “If the bee disappears from the surface of the earth, man would have no more than four years to live.”
Coral reefs follow the same path. They home a quarter of all marine fish species, and their extinction will affect the entire ocean ecosystem. Corals are dying mostly due to warming sea-surface temperatures and increasing acidification-both caused by human activities. Careless tourism, pollution, destructive fishing techniques, and coastal development helped to put corals in the endangered list of species. Today, about 19% of the world’s coral reefs are dead and beyond repair. Their extinction will compromise 500 million people that depend on coral reefs for their livelihoods.
For Each Lost Species, Comes Another Loss
The ecosystem falls apart when a single species is endangered. When we remove one element from any ecosystem, we provoke long-lasting effects on biodiversity. Fish depend on corals to live. Crops depend on bees pollination. We also depend on all species, animals, or plants, to keep our planet working in balance. We will lose water, land, and clean air if there are no healthy rivers, oceans, and forests. Humankind depends on healthy ecosystems to purify the environment.
Even our medicine depends on healthy ecosystems. More than 50% of the most used medications derived originally from plants. Yet, only 5% of the plants we know were tested for medical uses. Imagine how many thousands of plant species are waiting to be identified and studied. They could be the cure to many diseases scientists still search for.
Right now we are losing species at 1,000 to 10,000 times faster than the usual pace. Climate change alone is responsible for the loss of 50% of the global wild animal population. We are creating the biggest extinction since dinosaurs vanished from the planet. Note that dinosaurs have been gone for roughly 65 million years. We became the biggest threat to every living species, including ours.
Letting go even a slight strand in the web of life contributes to the falling of our planet’s sustainability, the crucial equilibrium that affects each and every one of us.