Birds and bats as biological control agents in macadamia: How distant we are? Implications of the shift in arthropod communities across a spatial gradient

Agriculture affects and depends on all other life support systems. It is becoming essential to achieve the global food demand without compromising ecological integrity. However, little is known about important ecological interactions in agroecosystems. Such systems represent particular reserves for biodiversity with associated ecosystem services. One of the key ecosystem services in agriculture is the top-down control of crop pests exerted by predators. A large number of insectivorous bird and bat species have been found to efficiently decrease pest pressure in several crops worldwide. Scarce information is found on how the distance from forested areas impacts such ecosystem services. To our knowledge, no information is available for macadamia crops. Our study is the first of a series that attempt to explore the potential of regional bird and bat species as biological control agents in macadamia. The results describe the arthropod communities in these systems across a spatial gradient between the forest and the orchard. The study was conducted in 31 sites around Bundaberg (Australia). Arthropods were collected in macadamia orchards using sweep-net and light-traps at fixed distances from forest patches at each site. Results showed that the abundance and richness of arthropods decreased in points further away from forests. Points closer to forested areas had more balanced communities with higher percentages of predators and parasitoids and lower percentages of herbivores than points further away. Further research is being conducted to understand whether differences in spatial composition of arthropod communities are associated with the foraging activity of birds and microbats. An opportunity exists to integrate wildlife in macadamia production, and to benefit both the farmers and the environment

Ecology and conservation of insectivorous bats in fragmented areas of macadamia production in eastern Australia

© 2016 Ecological Society of Australia Microbats perform important ecological services in agro-ecosystems, but several species are globally threatened by loss of roosting and breeding habitats. The successful conservation of bats in agricultural land requires adequate knowledge of their ecology. Using ultrasonic recorders, we studied the activity of insectivorous bats in areas of macadamia production in eastern Australia at two spatial scales: across woodland-orchard transects at the local scale and across three levels of fragmentation at the landscape scale. At the local scale, activity patterns of ‘clutter’ and ‘edge’ specialists were consistently higher in woodland patches, gradually decreasing towards isolated orchards, where only a few ‘open’ specialists were active. At the landscape scale, bat community activity was affected by the level of fragmentation, partly because three of the most recorded taxa (Austronomus australis, Saccolaimus flaviventris and Miniopterus australis) had their highest activity in less-fragmented areas. A distance-based model explained 24% of the bat community activity based on a combination of six environmental variables. Canonical correspondence analysis showed that a number of bat taxa were associated with open areas of macadamia, whereas other taxa were associated with increasing values of landscape composition, and arthropod and water availability. In addition, total bat activity was highly correlated with foraging rate. These results suggest that most bat taxa were influenced by proximity to woodland and the degree of fragmentation, and only few taxa were able to exploit isolated orchards. Environmental factors that promote bat activity could be exploited to strengthen conservation efforts. Preserving remnant woodland and promoting habitat heterogeneity will benefit several bat species. In particular, the foraging activity of ‘edge’ specialists could be fostered by increasing landscape connectivity and maintaining unobstructed water bodies near macadamia orchards. Considering that bats forage as they navigate these areas, conservation efforts could also bring benefits to farmers through pest-reduction services