The complexity of escosystems is so that we cannot study them without tripping over reductionism. Nor do we know what exactly happens in the set when we play a piece, for example eliminating an animal species.
Everything is connected with everything in a causal tangle so inextricable that a good example to begin to assume the fragment of high ground that the human being generated fortuitously in 1912.
Barro Colorado Island
In 1912 it was the moment at which, when the Panama Canal was built, the Gatun Lake. As a result of its rise in water, an elevated piece of land covered with tropical perennial forest was isolated from the rest of the earth.
This fragment of land was called Barro Colorado Island. In the long run, it ended up becoming a biological research station, as he explains Edward O. Wilson in his book Consilience:
In the decades that followed it became the ecosystem of its kind studied in greater detail in the world.
The size of the island it was only 17 square kilometers, therefore it was too small to keep jaguars and pumas. The prey of these big cats, large rodents called agoutis and bales, were thus free of their main cause of death: being devoured. These dams multiplied up to ten times their normal number:
They overexploited their food, which consists mainly of large seeds that fall from the forest vault, which caused a reduction in the reproduction and abundance of tree species that produce seeds.
The side effects soon appreciated. Since only trees with seeds were interested, and these were devoured through their seeds, small trees were favored, whose small seeds were not of interest to the Agoutis and bales. Suddenly, there were many small trees. This led, in turn, that animals that fed on small seeds also had an abundance of food, which caused them to reproduce exponentially.
The predators of these animals also increased. And so did the fungi and bacteria that parasitize small seed trees. The microscopic animals that eat these fungi and bacteria became denser. And the predators of those small animals also increased.
and so on through the trophic network and, in the opposite direction, as the ecosystem reverberated due to the restriction of its area and the consequent loss of its culinary carnivores.
Which we should make them reflect every time they tell us that an animal or plant species is in danger of extinction and public opinion only shuts down in response or limits itself to raising its shoulders.