Genetic
Genetic diversity is variation within and between species. Genes are the building blocks that determine how an organism will develop and what its traits and abilities will be. Genetic diversity plays an important role when it comes to adaptation if there are changes in an environment. More genetic diversity in a species or population means a greater ability for some of the individuals in it to adapt to changes in the environment, reports The Canadian Biodiversity Website.
Species
Species are perhaps the most well-known and the most distinct units of diversity. Each species can be considered to have a particular role in an ecosystem, so the addition or loss of single species may have consequences for the system as a whole. Species diversity ensures a balanced ecosystem, in which flora and fauna can maintain equilibrium without one species taking over and dominating. Interactions among organisms maintain diversity, and destroying or enhancing one species in a local ecosystem may destroy the whole system in time.
Ecosystems
Each system has an important role to play in the whole biosphere. Ecosystem diversity encompasses the variety of habitats that occur within a region. A good example is the variety of habitats that make up the San Francisco Bay-Delta ecosystem: grasslands, wetlands, rivers and estuaries. This level of biodiversity deals with all levels greater than species, such as communities, ecosystems and the interactions involved. This makes it difficult to study and even more difficult to predict outcomes.
Maintaining Equilibrium
Human activity is throwing many ecosystems out of balance and threatening the biodiversity of the entire planet, according to J. David Allan, professor of conservation biology and ecosystem management at the University of Michigan. Major threats, such as climate change, over-exploitation, species introduction, disrupted food chains and habitat destruction, are resulting in mass species extinction. When one element of an ecosystem is eliminated, the entire system comes under stress and becomes unbalanced. In many places, people have changed land-management practices to ensure the protection of species and land.