Improved management of farm dams increases vegetation cover, water quality, and macroinvertebrate biodiversity

Abstract

In many farming landscapes, aquatic features, such as wetlands, creeks, and dams, provide water for stock and irrigation, while also acting as habitat for a range of plants and animals. Indeed, some species threatened by land‐use change may otherwise be considerably rarer—or even suffer extinction—in the absence of these habitats. Therefore, a critical issue for the maintenance of biodiversity in agricultural landscapes is the extent to which the management of aquatic systems can promote the integration of agricultural production and biodiversity conservation. We completed a cross‐sectional study in southern New South Wales (southeastern Australia) to quantify the efficacy of two concurrently implemented management practices—partial revegetation and control of livestock grazing—aimed at enhancing the vegetation structure, biodiversity value, and water quality of farm dams. We found that excluding livestock for even short periods resulted in increased vegetation cover. Relative to unenhanced dams (such as those that remained unfenced), those that had been enhanced for several years were characterized by reduced levels of turbidity, nutrients, and fecal contamination. Enhanced dams also supported increased richness and abundance of macroinvertebrates. In contrast, unenhanced control dams tended to have high abundance of a few macroinvertebrate taxa. Notably, differences remained between the macroinvertebrate assemblages of enhanced dams and nearby “natural” waterbodies that we monitored as reference sites. While the biodiversity value of semilotic, natural waterbodies in the region cannot be replicated by artificial lentic systems, we consider the extensive system of farm dams in the region to represent a novel ecosystem that may nonetheless support some native macroinvertebrates. Our results show that management interventions such as fencing and grazing control can improve water quality in farm dams, improve vegetation structure around farm dams, and support greater abundance and diversity of aquatic macroinvertebrates.

Fencing farm dams to exclude livestock halves methane emissions and improves water quality

“…For the first finding, fenced farm dams recorded 32% less dissolved nitrogen, 39% less phosphorus, and 22% more dissolved oxygen than unfenced farm dams. Westgate et al (2022) is the only other study on this topic and showed comparable results to ours, with a 45–50% reduction in total nitrogen and phosphorus in fenced farm dams over unfenced farm dams, together with reduced turbidity and lower fecal contamination. The similar results between two field studies from different years (2019 and 2021) and seasons (summer and autumn) suggest that the positive effects of fencing on water quality may be maintained throughout the year.…”

“…For the first finding, fenced farm dams recorded 32% less dissolved nitrogen, 39% less phosphorus, and 22% more dissolved oxygen than unfenced farm dams. Westgate et al (2022) is the only other study on this topic and showed comparable results to ours, with a 45-50% reduction in total nitrogen and phosphorus in fenced farm dams over unfenced farm dams, together with reduced turbidity and S2 for all test statistics and Table S3 for importance scores). For the second finding, the higher water quality of fenced farm dams corresponded to 56% lower methane emissions (Figure 6).…”

“…Yet, the effects of installing fences (or any other management intervention) on farm dam GHG production remain untested. Similarly, there is little evidence of the benefits of farm dam fencing on water quality (Westgate et al, 2022). Hence, we here addressed two key questions: What are the effects of fencing farm dams on water quality (i.e., total dissolved nitrogen, total dissolved phosphorus, and dissolved oxygen), soil organic carbon, and GHG fluxes of methane and carbon dioxide? What are the mechanisms linking farm dam management to aquatic GHG fluxes? …”

“…Yet, the effects of installing fences (or any other management intervention) on farm dam GHG production remain untested. Similarly, there is little evidence of the benefits of farm dam fencing on water quality (Westgate et al, 2022). Hence, we here addressed two key questions:…”

“…Hazell et al, 2001;Lewis-Phillips et al, 2019;Westgate et al, 2022), investing in better farm dam management appears to be a promising strategy for improving farming productivity and environmental sustainability. Nevertheless, carbon cycles in farm dams remain one of the least explored among freshwater systems.Promising avenues for follow-up studies include environmental work to analyze long-term cycles for several carbon pathways (e.g., methane ebullition, plant-mediated methane emissions, rate of carbon sedimentation), economic assessments to determine the best allocation of incentives for sustainable management interventions, and social studies to establish non-market benefits and farmers' willingness to adopt management interventions.…”