Every ecosystem is incredibly complex and even one change can have a detrimental effect on a whole range of organisms.
Here is just one simple example:
Since the 1960’s, cod populations in UK waters have seen a steady decline. Two reasons for this decline are regarded as plausible:
Now comes the twist.
Herring is a food source for cod, so inevitably fewer cod means more herring, and guess what more herring eat? More young cod and cod spawn, so even less cod.
Nothing in the natural world is as simple as 2+2 = 4. We will have to start thinking on a much broader plane if we want to understand the effects of global warming.« 200 year old tree shows ‘strong tolerance’ to Ash Dieback disease | How much CO₂ can you save by making a few simple lifestyle changes? »