My Lords, in supporting the amendment from the noble Lord, Lord Teverson, I draw attention to a particular feature that has been mentioned but perhaps could be made more explicit. It is a feature of both the climate emergency and the biodiversity emergency: the discontinuities that will arise as a result of incremental change. My noble friend Lady Boycott alluded to this in talking about the rivets in an aeroplane: it does not matter, perhaps, if one, two or three rivets fall out, but when more than a critical number fall off there is a discontinuity and the plane falls out of the sky. This is true, as we know from the IPCC and others, of the climate emergency. We hear over and over of the notion of dangerous climate change, whereby if we exceed a certain boundary then we will tip into a new world in which life becomes intolerable and many regions of the planet are uninhabitable for the human species. That is equally true of the biodiversity emergency.
I am an academic ecologist, and so I will refer back to the scientific literature. Back in 1969, an American ecologist, Robert T Paine of the University of Washington, drew attention to the notion of keystone species. He was studying a species of starfish that lives in the
intertidal zone of the north-western United States—Washington state. If this species of starfish disappears then the whole ecosystem flips to a new state, because the starfish is the keystone species that maintains the equilibrium of the intertidal ecosystem. The same will be true in many other situations.
It is not just the number of rivets that fall out of the plane that is important; it is particular, key rivets. The sad thing is that, if we lose some of these keystone species, we will be among the ones that suffer, because we will suddenly find that the systems we rely on to produce food, purify our water and provide other ecosystem services will simply not exist any more. A genuine emergency is created by crossing these thresholds: once we have crossed them, it will be too late.