Old growth, regrowth, and planted woodland provide complementary habitat for threatened woodland birds on farms

A central challenge for threatened species conservation in agricultural landscapes is to understand the relative contributions of old growth, regrowth, and planted woodland to species persistence. We offer a new perspective into solving this problem by using a systematic conservation planning approach to integrate spatial biodiversity and economic information with patch complementarity. We applied this to an eight-year study of woodland birds vulnerable to extinction across an extensive agricultural region of Australia. We used regression and ordination analyses to show that species were more likely to occur in regrowth and old growth woodland patches compared with plantings. We then set objectives of finding sets of complementary patches for supporting species across the landscape, and explored biodiversity trade-offs resulting from production- or cost-focused objectives. We found that species persistence could be achieved only through sets of patches containing all patch types (old growth, regrowth, plantings). Scenarios that selected sets of patches irrespective of patch type maximized species occurrence over time for the lowest combined area and establishment costs. Patch sets had a higher proportion of plantings for the objective of minimizing area, but a more equal proportion of patch types for the objective of minimizing cost. Our findings demonstrate what the relative composition of old growth, regrowth, and plantings should be when considering vegetation management interventions for threatened species conservation. Government policy and associated funding aimed at improving biodiversity conservation in agricultural landscapes needs to promote both regrowth woodland and revegetation planting strategies in addition to old growth woodland protection.