How much biodiversity is enough in agricultural landscapes?

Agricultural intensification is known to reduce biodiversity values at landscape scales. Many researchers have proposed targets for the retention of native vegetation to maintain a functioning landscape. The geography of the land (slope, aspect, altitude) and land capability (geography plus soil type and availability of water) have determined where investment in agriculture has been directed, i.e. flat sites on fertile soils. In a topographically variable State like Tasmania, with over 40% of its land area in reserves, it is understandable that public perception is that we have ‘enough’ biodiversity. As ecologists we know that communities and species are over or under-represented in the reserve system and in the landscape as a whole. The development of irrigation infrastructure will change land capability assessments as restrictions relating to water availability are addressed. High cost irrigation infrastructure demands high value crops to be grown under irrigation. Wine grapes and cherries are two such crops which are likely to impact on traditional dryland native grazing areas such as hillslopes. This paper discusses how native species and communities may be further fragmented in the future in the context of investment in irrigation development, and what the potential impacts on ecosystem service provision may be.