Humans reduce the amount of land available for other animals and plants by building, quarrying, farming and dumping waste. When a habitat is taken over for these uses, the species that lived there lose their home, and biodiversity can fall.
Peat bogs are a good example. Peat is dug up and sold to make garden compost. Destroying peat bogs and other areas of peat reduces the area of this habitat, and so reduces the variety of plant, animal and microorganism species that live there. Also, when peat decays or is burned, it releases carbon dioxide into the atmosphere, which contributes to global warming.
There is a conflict here. Cheap, available compost helps to increase food production. But peat bogs and peatlands need to be conserved as habitats for biodiversity, and to reduce carbon dioxide emissions. People have to balance these needs.