But you are talking about two different subjects, which are linked but they are very different impacts. Not using a car to tackle climate change is different than destroying bio-diversity.
Take birds for instance There are over 600 million fewer birds in Europe than there were 40 years ago, with House sparrow populations declining by half. Mainly due to habitat loss and man made actions.
Plastic lawns remove worms, burrowing insects and bees from the birds diet, they cannot forage for young, they have ZERO resource for wildlife. You are instantly depriving nature of part of the intrinsic web of life.
Even with paves areas, you still have burrowing insects and ants, etc..
Plastic lawns not only have a huge carbon footprint which is a long term affect, but they have a huge instant affect in biodiversity right now and that's is and immediate problem. We are currently experiencing the planets 6 mass extinction caused by man, since the dawn of human civilization, 83% of wild mammals, 80% of marine mammals, 50% of plants and 15% of fish have vanished.
Many species of animals, need connectivity to travel to breeding sites and to feed ect. Take a Great crested new for example, it spends 85% of its life on land and only uses ponds to breed. They can transvers natural grass as it contains moisture and shade, plastic lawns contain chemicals that are absorbed by their skin and heat us massively in warm weather making them a death trap.
This is not just about carbon there is a bigger picture.