Moaning about monocultures

The National Arboretum of Canberra is a beautiful and unique place. Just one of the things that makes it unique is its design of planting small "forests" of a single species - there are about 100 of these 1 - 3 ha single species "forests" over the 250 ha arboretum. When people hear about this design though, many exclaim in apparent horror and ask why we countenanced the planting of monocultures! Monocultures are apparently the antithesis of biodiversity or of "naturalness" and should have been shunned.

But ...monocultures are not unnatural. In shade intolerant and pioneer species like many of the eucalypts, areas considerably in excess of 3 ha, or even 250 ha may contain only one tree species like Alpine Ash after a hot fire. It is extremely common for a single tree species to exclusively dominate just 1 ha in a native forests in Australia as well as in many other parts of the world.

Further, "biodiversity" has three scales - an ecosystem scale; a species scale and a gene scale. At the species scale, 100 tree species in 250 ha is actually pretty impressive, but it is at the gene scale that the. National Arboretum of Canberra really shines for biodiversity. Having 1 - 3 ha of the same species all planted together means there may be a hundred or more individual trees growing in a consistent, well maintained and observable location. This is extremely rare anywhere in the world and provides one of the few opportunities to quantify and appreciate genetic diversity. Given the high proportion of tree species classified as rare or threatened, this opportunity to study genetic biodiversity is of even greater significance.

So, caste off any lingering and ill formed angst over small areas of monoculture and celebrate the potential for the National Arboretum of Canberra to provide valuable information at multiple scales of biodiversity.