Explanation
1. Statement 1 is correct. Global warming leads to climate change, altering temperature and precipitation patterns, causing sea-level rise, and increasing the frequency of extreme weather events. These changes can exceed the tolerance limits of many species, leading to shifts in range, phenology changes, and extinctions, thus posing a significant threat to biodiversity.
2. Statement 2 is correct. Fragmentation of habitat, caused by human activities like agriculture, urbanization, and infrastructure development, breaks large, continuous habitats into smaller, isolated patches. This reduces the total area available for species, isolates populations, restricts gene flow, increases edge effects, and makes species more vulnerable to local extinction, thereby threatening biodiversity.
3. Statement 3 is correct. Invasion of alien species (non-native or exotic species) introduced into a new geographical area can outcompete native species for resources, prey upon them, introduce diseases, or alter the habitat structure. This is a major driver of biodiversity loss worldwide.
4. Statement 4 is incorrect. The promotion of vegetarianism generally reduces the environmental footprint associated with livestock farming (e.g., land use for grazing/feed production, greenhouse gas emissions). While dietary shifts have complex ecological consequences, the direct promotion of vegetarianism itself is not considered a threat to biodiversity; rather, it is often seen as potentially beneficial or neutral.
5. Therefore, Global warming, Fragmentation of habitat, and Invasion of alien species are recognized threats to biodiversity.