Evolution leads to an increasing number of species, and that's why it is so difficult for us to know how many of them inhabit the Earth. Should we spend efforts to conserve all of them or would it be enough with just a few?
Nature establishes relationships between species and organisms, forming a very complex network where often great-interconnected nodes appear. They are called 'hubs'. But humans also create this kind of networks, such as airports as nodes and flights as connections.
Some giant trees, such as cedars and redwoods, are an example of great longevity and their populations depend much more on tendencies than on specific traumatic episodes. Climate change and human pressures can put their survival at risk.