Sustainable Farms

Please see my CV for a full and up-to-date list of publications.

Integration by case, place and process: Transdisciplinary research for sustainable grazing in the Lachlan river catchment, Australia. Landscape Ecology in press.

This paper highlights tensions between the trajectory of tree cover in the region and stakeholder values. Under status quo management, many scattered and isolated paddock trees will be lost from farms, although most farmers would like to see them persist. Case studies on selected farms reveal management strategies that may be more sustainable in terms of tree regeneration and agricultural productivity, such as rotational grazing. In addition to these applied insights, our work provides a case study illustrating how a transdisciplinary study can be conducted efficiently by a small team. Our pragmatic approach has successfully combined targeted disciplinary activities with strategic collaborations and stakeholder engagement, all united by shared landscape, case graziers, and outreach activities.

The disproportionate value of paddock trees, Biological Conservation, Vol. 143, No. 6, pp. 1564-1567 (2010).

We empirically demonstrate the disproportionate value of scattered trees for birds and bats in an Australian livestock grazing landscape. We surveyed birds at 108 sites and bats at 63 sites. Sites spanned the full range of tree densities in the study area, from zero to over 100 trees per hectare. The marginal value of individual trees was highest when trees occurred at low densities. Compared to treeless sites, bird richness doubled with the presence of the first tree; bat richness tripled with the presence of 3–5 trees; and bat activity increased by a factor of 100 with the presence of 3–5 trees. Thereafter, the marginal effect of additional trees on birds and bats diminished rapidly. Although specialist species were restricted to large areas of dense tree cover, scattered trees effectively maintained moderate levels of bird and bat activity throughout largely cleared parts of the landscape. Future management activities should recognize the disproportionate value of scattered trees.

Using photography to elicit grazier values and management practices relating to tree survival and recruitment , Land Use Policy, Vol. 27, No. 4, pp. 1056-1067 (2010).

We asked graziers to photograph significant features on their properties, and used the images as prompts in later interviews. This elicited graziers’ landscape values and other drivers of their management practices related to tree cover. The targets that our 25 case landholders chose to photograph, and the ways they discussed them in later interviews, reflected the focus of past education and incentive programs, suggesting that well-designed policies, educational messages and incentives do seem to reach landholders and result in improved practices. For example, many landholders reported management activities related to the protection of large woodland patches or the maintenance of coarse woody debris. The maintenance of scattered tree cover has not been a focus of policy initiatives in the past. Despite this, the narratives elicited by photos of isolated and scattered trees showed graziers valued them and were aware of and concerned about their decline, yet lacked knowledge about how to protect and regenerate them. Graziers urgently need unambiguous advice and practical assistance to help them adapt their practices to maintain scattered trees in the long term.

Toward landscape-wide conservation outcomes in Australia’s temperate grazing region, Frontiers in Ecology and the Environment, Vol. 8, No. 2, pp. 69-74 (2010).

Agriculture and livestock grazing threaten biodiversity around the world. In the grazing landscapes of eastern Australia, a common conservation strategy has been to exclude livestock from large patches of trees (typically > 5 ha). This has major local benefits, but is unlikely to stem regional biodiversity loss. Using a case study from the Upper Lachlan catchment in New South Wales, we show that (1) approximately 30% of tree cover occurs as very small patches or scattered trees; (2) large patches have disappeared from 90% of the landscape; and (3) large patches are 3.5 times more likely to be in unproductive upland areas than in lowland areas of high conservation concern. Given the limitations of focusing on large patches of trees to achieve regional conservation outcomes, the next generation of conservation initiatives should consider a new suite of additional measures that could deliver biodiversity benefits across broad areas of the region. Two key measures that must be considered are new incentives for farmers to alter livestock grazing practices and reduced fertilizer use.

Reversing a tree regeneration crisis in an endangered ecoregion, Proceedings of the National Academy of Sciences, Vol. 106, No. 25, 10386-10391 (2009). PDF FREELY AVAILABLE.

By using remotely sensed data on tree cover and extensive field data on livestock grazing regimes, soil chemistry, tree diameters, and tree regeneration, we show that our study region is facing a tree regeneration crisis. Under conventional management, across the region, millions of hectares of land currently supporting tens of millions of trees will be treeless within decades from now. This would have severe negative ramifications for biodiversity and key ecosystem services, including water infiltration and shade provision for livestock. However, we identified an unexpected win–win solution for tree regeneration and commercial grazing. A relatively new practice in the region is fast-rotational grazing, characterized by prolonged rest periods in between short, intensive grazing events. The probability of regeneration under fast-rotational grazing was up to 4-fold higher than under conventional grazing, and it did not differ significantly from the probability of regeneration in ungrazed areas. In addition, trees were more likely to regenerate where soil nutrient levels were low. These findings suggest that the tree regeneration crisis can be reversed by applying low-input, fast-rotational grazing. New policy settings supporting these practices could signal a turning point for the region, from ecological decline to ecological recovery.

Tree decline and the future of Australian farmland biodiversity, Proceedings of the National Academy of Sciences online early (2010). PDF FREELY AVAILABLE.

Farmland biodiversity is greatly enhanced by the presence of trees. However, farmland trees are declining worldwide, including in North America, Central America, and parts of southern Europe. We show that tree decline and its likely consequences are particularly severe in Australia's temperate agricultural zone, which is a threatened ecoregion. Using field data on trees, remotely sensed imagery, and a demographic model for trees, we predict that by 2100, the number of trees on an average farm will contract to two-thirds of its present level. Statistical habitat models suggest that this tree decline will negatively affect many currently common animal species, with predicted declines in birds and bats of up to 50% by 2100. Declines were predicted for 24 of 32 bird species modeled and for all of six bat species modeled. Widespread declines in trees, birds, and bats may lead to a reduction in economically important ecosystem services such as shade provision for livestock and pest control. Moreover, many other species for which we have no empirical data also depend on trees, suggesting that fundamental changes in ecosystem functioning are likely. We conclude that Australia's temperate agricultural zone has crossed a threshold and no longer functions as a self-sustaining woodland ecosystem. A regime shift is occurring, with a woodland system deteriorating into a treeless pasture system. Management options exist to reverse tree decline, but new policy settings are required to encourage their widespread adoption.