One of the best ways to increase the resilience of an ecosystem is to increase the diversity of organisms. This is because every species (and individual) responds differently to disturbances. A community with low diversity risks being wiped out by a single disturbance event, whereas higher species diversity gives a greater chance that some individuals will survive and allow the rest of the community to recover. Where bushland has experience prolonged or severe disturbances, species diversity tends to be low. In such cases it can be beneficial to boost species diversity by importing appropriate plants from nearby areas.
Species Enrichment is not appropriate for all situations. On the spectrum of restoration techniques, Species Enrichment sits at the more disturbed end of Assisted Regeneration, but before Reconstruction is required. Resilient bushland with undisturbed soils generally contain a diverse range of species either as growing plants, or as dormant seeds in the soil and do not require plantings.
Situations where Species Enrichment can be useful are:
- Where a native canopy remains, with little or no understorey layers, such as areas with a history of mowing
- Areas with long-term weed infestations where the soil seed bank has been depleted (e.g. dense Privet stands)
- Edges of bushland where soils are disturbed from road works or construction activities
There are several important points to consider when selecting plant material for species enrichment. The main ones are:
- Plant material should be collected from as near as possible to the site (provenance) and from a similar vegetation community
- Selected species should fill a niche not currently occupied by native species (e.g. compete with or displace a weed infestation, provide an understorey layer, replace canopy species that are not recruiting new individuals)
- Species should suit the current conditions of the site – often changes to site features such as drainage or fire frequencies or light levels mean that species assemblages will shift to a different community type