Forests are ...................... hot spots.
Forests are biodiversity hotspots. Hotspots are the areas which are extremely rich in biodiversity. They are habitats for a diverse group of species of plants, animals and microorganisms. They are under constant threat due to climate change and habitat loss. All forests are not biodiversity hotspots. A characteristic feature of hotspots is high degree of endemism. Tropical rain forests are richest ecosystems in terms of diversity of vegetation.
So, the correct answer is 'biodiversity'.