Biological diversity is often divided into three main groups when it is assessed. These are ecosystem diversity, species diversity and genetic diversity. They of course work across a variety of scales, with ecosystem diversity generally be concerned with landscapes, species diversity often considered at the scale of an individual forest, and genetic diversity considered at the scale of a stand. There are however exceptions to this, particularly with genetic diversity, which is increasingly concerned with the number and geographic distribution of forest-associated species at risk of losing genetic variation or which are locally adapted.
Concern has largely focused on species that are endangered in some way. The International Union for the Conservation of Nature, also known as the World Conservation Union, but recognized everywhere as simply the IUCN has developed an important system for the classification of species in danger, known as the Red List (see: http://www.iucnredlist.org/). This is an international scale, and takes an international perspective. Other systems exist, and any jurisdiction can assess the degree of endangerment of the species present. This can create problems, as species ranges do not follow political boundaries. Many of Canada’s endangered species, for example, are relatively common in the USA, but their ranges just reach over the boundary into Canada.
The biggest concerns around biodiversity are associated with the degradation of forests and deforestation. A high proportion of forest-dependent mammals are endangered, as are many other organisms, although some groups, such as the invertebrates, are barely understood. Forests range from intact, in a largely natural state, to highly fragmented or even completely lost. The impacts on biodiversity vary accordingly.
Forest health is closely related to biodiversity. Maintaining forest health has proven extremely difficult, and human activities have exacerbated many situations. In a world of climate change and increased international trade, forest health will become even more difficult to maintain, and will require constant vigilance. Problems can go unnoticed until they reach crisis proportions, although events in the recent past have made forest authorities more aware of the risks that they face. Forest managers have a major role to play in maintaining the health of the forests in their care, and need to be aware of all the potential threats that those forests face.