For about 150 years, we have known how species evolve.
The big question is whether a sixth great extinction, this one caused by man, is now under way.Counting backwardsTo assess the impact of humanity on biodiversity, you need to know how many species there are on the planet, and how many species have gone extinct in recent years.
It is a graphic portrayal of the vast number of species disappearing from the planet; a difficult calculation, as scientists don't know how many species there are, with estimates ranging from two to 50 million.
We will not know how many species exist off Alaska until a major effort is made to combine and reconcile species lists and then "ground-truth," or verify, identifications using accurate, scientifically acceptable taxonomic guides.
We don't even know how many species of fungi there are on Earth.
What makes it so difficult to know how many species share our planet?
"No, we are traders and we know how the species dies and reproduces itself.
We cannot know how many species we live with until we have solid definitions and systems for identifying them.
In the middle of a mass extinction, he says, it's useful to know how many species there were to start.
Moreover, it is necessary to know how tree species respond to the two main limitations in these areas: microsite availability (i.e., roadslope characteristics) and seed arrival, which is related to propagule source, dispersion vector and landscape characteristics.
