The correct option, 1, 2, and 3 only, identifies threats to biodiversity stemming from global warming, habitat fragmentation, and the invasion of alien species. Global warming leads to changes in climate that can disrupt ecosystems and species' habitats, while habitat fragmentation reduces the size and connectivity of ecosystems, often making it difficult for species to survive and reproduce. The invasion of alien species can outcompete native species for resources, leading to declines or extinctions of indigenous biodiversity. In contrast, the promotion of vegetarianism is generally seen as a conservation strategy that can reduce pressure on ecosystems and biodiversity by lowering the demand for livestock agriculture, making it a positive rather than a negative influence.