How can we mitigate species loss?
Stop destroying habitat seems to be the most effective approach.
More protected areas, like national parks, would help as right now the total world protected areas are quite small. Marine ecosystems also need protecting too.
Environmentalist often focus on large loveable iconic species, like the African elephant in their campaigns. This has an added benefits of not only helping to reduce elephants losses, but if a protected area is set aside for elephants, it also protects hundreds of other species - acts kind of like an umbrella protection scheme.