Agricultural landscapes in south-eastern Australia are largely cleared of native vegetation, with whatever remains surviving in small, isolated remnants surrounded by a sea of livestock grazing and/or industrial cropping. To explore the effectiveness of replanted areas for maintaining biodiversity and how landholder attitudes influence restoration outcomes, we undertook a study in the Wimmera and Benalla regions of north-west and north-east Victoria, Australia. These areas have been heavily cleared over the past 150 years, with less than 10% of native vegetation remaining in many areas. Habitat restoration such as the revegetation of low quality agricultural land has been occurring in these regions for approximately 15 years, mainly for conservation purposes, but little research has been undertaken to show the biodiversity benefits of these replanted areas.
Our study looked at how reptiles (Reptilia) and beetles (Coleoptera) responded to the type of the sampled area (remnant, revegetated or cleared), the shape of the sampled area (linear strip or patch) and interactions between shape and type. Reptiles and beetles are less studied than other animals, because it takes a lot of survey effort, usually in very hot and dry conditions, to get enough data to understand how these fauna respond to changes in the landscape. Despite survey difficulties, reptiles and beetles provide many important functions in the environment, and respond differently to landscape changes as they are less mobile than other animals, such as birds. Our study also determined landholder attitudes towards revegetation, and how they managed remnant areas and restored habitat on their property. Research that incorporates both social and ecological components seldom occurs, but we felt it was important to get an understanding of both to provide meaningful management recommendations to practitioners and the community more generally.
Our results didn’t bode well for native fauna in these highly modified agricultural areas. We found that, although a robust subset of reptile and beetle communities remained in all of the habitat types we surveyed, more specialised species had largely been lost, with some species reliant on high quality habitat remaining in remnant linear strips along roadsides (>20m wide). These areas were less likely to be grazed by livestock and probably received more water from runoff, increasing plant growth. Interestingly, rarer reptiles were more likely to be located along remnant roadsides further away from patches of habitat. We found revegetated areas lacked the ground layers normally found in the grassy woodlands that would have once dominated this landscape, such as native herbs and grasses, leaf litter, fallen timber and rocks. These habitat elements are important to maintain or entice rarer reptiles and beetles into restored areas.
The social side of our study showed that landholders, especially those in a Landcare group or those less reliant upon on-farm income, were more likely to undertake restoration activities. Landcare is a community-based natural resource management group that is responsible for many of the environmental works on private land. However, most landholders were more likely to manage restored and remnant areas if they perceived threats such as weeds, pests and fire risk would negatively impact their property, than to enhance environmental outcomes.
To integrate this social and ecological data and expert opinion, we used a graphical cause and effect model called a Bayesian Network to determine the most cost-effective management actions to increase biodiversity, or in this case reptile and beetle species richness. Restoring cleared habitats was always more cost-effective than managing remnants or previously replanted areas, because of the higher marginal benefits that arise from restoring degraded habitats. Replanting trees and shrubs, restoring litter, timber and rocks, and undertaking weed control were the most cost-effective management actions as they provided the greatest benefit to ground dwelling animals such as reptiles and beetles. On a landscape scale, restoring cleared areas will benefit farms by reducing wind and water damage to crops and livestock, and increasing ecosystem services such as land aesthetics, natural pest control and crop pollination. Explaining these multiple and integrated social, ecological and economic benefits to rural communities may help to get more people involved in restoration activities.
If our current range of restoration methods are not maintaining native fauna, what other methods will accomplish this? Are landholders likely to manage remnant and restored habitats effectively if practitioners do not understand concerns about how these areas influence productivity?
Photos: Sacha Jellinek, University of Melbourne’s Centre of Excellence for Environmental Decisions