Does habitat quality reflect insect diversity?
Assessments of the quality of native vegetation are commonplace in ecological studies and in the planning process, whereby comparisons are made between existing vegetation and those of benchmarks representing an undisturbed condition, with larger patches and patches of vegetation with structural complexity receiving a higher score. However, it is not known whether insects that occupy smaller spatial scales are affected by size or structure in the same manner as vertebrates. Additionally, there is very little information on how the fragmentation process affects ecosystem services performed by insects, such as pollination and pest control which are vital for ecosystem functioning nor at which stage of degradation is this threshold crossed. This paper outlines a study undertaken in Grey-Box Grassy woodlands investigating insect diversity, abundance and functionality in remnants of various sizes; small (< 5 ha), medium (6-12 ha) and large (17-50 ha) and within remnants with varying degrees of habitat structure ranging from near natural (State 1) to highly degraded (State 5). Whilst the size of the remnant had no influence on insect diversity or abundance, remnants with greater habitat structural diversity contained more species and individuals of insects, and therefore a probable increased rate of ecosystem services to the surrounding agricultural landscape. Whilst diversity of insects declined with increasing disturbance there was also a change in species composition particularly evident in State 2 to State 3 resulting in an overall decrease in the number of pollinators and predators. These preliminary results suggests that smaller tracts of remnants with more structural diversity could potentially be more valuable on farms in terms of pollination and pest control than large remnants without structural diversity. However, longer-term studies and more replicates are required to confirm this work.