Humans sit at the top of the food chain. Humans are overpopulated, voracious, wasteful, effective and globally transient in decimating species, habitats and links in the food chain at a rate that will eventually result in the death of hundreds of millions of humans. Human populations are also booming because humans are adept at decimating or eradicating living things that are annoyances or threats to humans.
Humans not only kill the food that is desired, humans kill the food chains and the habitats.
Human populations are booming while the habitats and populations of species that need food and that serve as food are being wiped out to the point of inability to regenerate. Imbalances in the predatory/prey dynamic begin with humans, but human predation is so indiscriminate that it continues to the bottom of the food chain as large fish, large trees, invertebratesand even microscopic creatures find the balance of life: habitat, prey and predators, put entirely out of whack.
While we have considered a particular species as near or complete in extinction, there may have been many species of the same living thing that were decimated, due to minute or not so obvious little adaptations that have been made.
Humans are responsible for the "irreversable loss of biodiversity of life on Earth" (1) atthe estimated rate of 10 to 30 percent of amphibian, mammalian and bird species. In about three decades, human activity is associated with the decline of about 1/3 of the vertebrate species of Earth.
While the species and habitats of the Earth are enormously resourceful in ability to regenerate, humans are now at the point of flipping the planet to the point of inability to regenerate after suffering the damage that humans cause. The food chains are being permanently disrupted to the point of no repair.
As coral reefs are damaged, infected or destroyed by human activity, the massive amount of life that feeds from the nutrient of coral reefs or that uses them for habitats is put at risk.
As forests are destroyed, the massive amount of life that is supported by forest habitats is put at risk and unique, localy dependent lifeforms are extincted. As development occurs, migrating birds cannot find nesting or resting places and are hunted to extinction. As alien species are brought past natural boundaries, local species cannot defend themselves and are decimated or replaced by the far more aggressive alien species.
As the open ocean is polluted or overfished, the delicate balance of aquatic habitat and spare surface life is destroyed. Desalination of brackish and sea water to provide fresh water for human developments molests the habitat for much of the world's food and even fertilizer for growing food.
It is much more than the desirablefish that are captured killed or destroyed in commercial fishing operations that become more and more effective and indiscriminate at hunting and killing desired fish as well as their associated and supporting life forms.
Biodiversity allows for species to adapt to reasonable and natural changes in habitat and environment. As a forest burns, the living creatures that can escape find other habitats, migrating back to the original grounds once the forest regenerates. In that migration and re-migration, there may be minute changes in particular members of species. Fish can relocate to other parts of the ocean and make evolutionary adaptions when a natural threat occurs and then resolves itself.
Biodiversity allows a species to feed on one thing then another, rather than eating everything in sight until there is nothing left to eat. The Earth has a remarkable capacity to heal itself, to re-establish habitats and to allow even the lowest parts of the food chain to regenerate and to achieve balance.
With humans, the capacity is reversed. Humans have outstripped the ability of the Earth to regenerate after such massive damage to habitats, populations of the most minute parts of the food chain and to the balance between predator and prey.
As a result, humans will die out simply because, like the dinosaurs, they are too effective as top predators. Until the human population returns to a better balance with the planet's ability to tolerate them, there will be a major correction. But with so much irreversible extinction of important parts of the food chain, the Earth may never be able to support as many humans again.
Anup Shah, "Loss of Biodiversity and Extinctions", Global Issues, December 2009