Climate Change

Climate change would seem to have been linked to many, if not all, mass extinctions, although this may have been accompanied by other extinction motors or have been caused by them.
All species are dependent on and adapted to the climatic conditions of their ecosystem distribution. Every known corner of our planet is inhabited by some living creature which survives and prospers in that environment. There are bacteria, Archaea¹³, living near volcanic vents at 88C (190F) - nearly boiling - and corrosive acid conditions (pH=3.5) approaching the sulfuric acid found in a car battery (pH=2). Polar bears live in Arctic conditions of -30C. Zooplankton¹² live at 5,000m (16,500 ft) below the surface of the oceans where pressure is immense. The Albatross can stay airborn for ten months and Whooper Swans have been seen at an altitude of 29,000ft.
Species occupy their ecological niche which may have very general or highly specific parameters. Those species or taxa which have colonised a particular environment and have selective feeding habits will be more likely to be susceptible to changes in their ecosystem than generalists.

The genus Pavo has two extant species, Pavo cristatus and Pavo muticus. The two species diverged about 70,000 years ago just after the time of the Toba volcanic eruption. Today the common Blue Peacock, Pavo cristatus, has been introduced all over the world and can withstand extremes of heat and cold without much difficulty. In contrast, the sibling species, Pavo muticus, known as the Green Peafowl (this one on the bottom photo is from the subspecies Pavo muticus imperator), which is a tropical forest dweller cannot endure temperatures at or below freezing for more than a very short time and any significant lowering of its habitat temperature would lead to extinction. Fortunately we are expecting the world to get warmer, not colder.

Even though species themselves may be able to withstand temperature or rainfall change, they may be dependent on other species for food which are not so resilient and thereby die out. The food chain or food web¹⁴ factor is vital for all animals, including humans, and is inherently fragile. The extinction of one species could create a gap in the food web which had consequences for the survival of another, perhaps thousands of miles away. The extinction of the American Megafauna is thought to be due to a change in vegetation; first the herbivors and then the predators died out.
Human history has been greatly influenced by climate change and humanity is currently trying to come to terms with its possible involvement in compounding natural processes. This will be discussed later.