Ecological and anthropomorphic factors permitting low-risk assisted colonization in temperate grassy woodlands

There is a risk that the potential of assisted colonization to contribute to biodiversity conservation will be lost in the storm of controversy that currently surrounds it. This paper describes a low-risk scenario for assisted colonization using plants. Using an analysis of temperate grassy woodlands from Australia, relevant ecosystem attributes are identified which make assisted colonization a sensible strategy, and that may characterize other favorable situations globally. The contributing elements include: a biota adapted to resource conservatism, a naturally connected landscape with component species having wide distributions over a large climatic gradient, current land use unrelated to endogenous disturbance regimes resulting in extensive replacement and modification of the ecosystem over its entire range. Intensive agriculture can create a highly-disturbed and nutrient-enriched landscape matrix, which effectively fragments the species assemblage. Relocation of plant species within and close to their range is not going to create an invasive situation in these landscapes. Candidates for assisted colonization are forbs and interstitial grasses that have persisted over much of their range, but which have declined within that range due to land use impacts. The suggested priority receiving sites would be those with a moderate level of past modifications, now being managed for conservation and with low nutrient status. The proposed use of assisted colonization is a conservative strategy that will build on current conservation practice and greatly improve the prospects for native plants where climate change is superimposed on a fragmented plant community.