Presentation: Biodiversity (II)

Abstract

ossil information shows that species diversity has increased steadily since the emergence of life about 3,500 million years ago. The number of species of terrestrial plants has progressed in an inexorable growth, punctually interrupted by natural catastrophes since its evolution, somewhere on the banks of a freshwater course in the Upper / Lower Ordovician Carbon. There have never coexisted as many species of living beings and plants on Earth as in the Holocene (last 11,500 years). This means that, on average, the rate of speciation was naturally higher than the rate of extinction, although permeated by catastrophic events. In science, concepts are more or less consistent, and theories and hypotheses corroborated (confirmed) or refuted (deleted) on the basis of observational and / or experimental evidence. Scientists and non-scientists are free to propose alternative explanations, but in science no one escapes the tyranny of facts: anyone who defies a hypothesis or a theory has to prove that the data supporting them are wrong or propose plausible alternative explanations, available evidence. The definitive rejection of a theory depends on the scrupulous fulfillment of one of these two conditions. In a time of relativization of evidence and science, and in particular of the science of biodiversity, it is crucial to bear in mind that the formidable body of observations accumulated over the last decade shows in a peremptory way that the terrestrial biota faces a new mass extinction, this time mediated by an unusually successful species: the man.