Environmental degradation is eroding arable land and there is a looming energy crisis.

It is harder for farmland birds to breed in the monocultural habitats that now characterise much arable land.

They also argue that, contrary to popular belief, we are not running out of arable land.

Why use a third of the world's arable land to grow soya and other cereals to feed farm animals when they could graze in fields?

And algae can be raised on land that is not suitable for farming, avoiding arguments about using arable land to produce fuel.