Biology subjects

Milner-Gulland, E. J.

Publications and source records attributed to Milner-Gulland, E. J..

4 recordsLinked to original sources

bioRxiv2024

Metrics based on habitat area and condition are poor proxies for invertebrate biodiversity

There is increasing demand for standardised, easy-to-use metrics to assess progress towards achieving biodiversity targets and the effectiveness of ecological compensation schemes. Biodiversity metrics based on combining habitat area and habitat condition scores are proliferating rapidly, but there is limited evidence on how they relate to ecological outcomes. Here, we test the relationship between the statutory biodiversity metric used for Biodiversity Net Gain (BNG) in England -- and as the basis for new biodiversity credit systems around the world -- and invertebrate richness, abundance, and community composition. We find that the combined area-condition BNG metric does not capture the value of arable farmland and grassland sites for invertebrate biodiversity: invertebrate communities were highly variable across sites that had the same type and condition under the BNG metric. We found no reliable relationship between scores under the metric and either invertebrate abundance or species richness, with the risk of the metric undervaluing sites of high invertebrate value. Our results highlight the need to incorporate factors beyond habitat type and condition into site evaluations, and to complement metric use with species-based surveys.

ecology↗

bioRxiv2021

The role of nature conservation and commercial farming in psychological distress among rural Ugandans

Mental illness is a leading contributor to the global burden of disease, but there is limited understanding of how it is influenced by socio-ecological context, particularly in the global south. We asked how interactions with ecological systems influence stressors associated with psychological distress in a rural Ugandan case study. We conducted and thematically analyzed 45 semi-structured interviews with residents of Nyabyeya Parish, Masindi District. Our results suggest that poverty and food insecurity were the primary reported causes of "thinking too much" and related idioms of psychological distress. The expansion of commercial agriculture may have been associated with the contraction of subsistence farming, reportedly exacerbating poverty and food insecurity among poorer households but contributing incomes to wealthier ones. Furthermore, households bordering a conservation area reported that crop losses from wildlife contributed to food insecurity. However, forest resources were important safety nets for those facing poverty and food insecurity. Our study suggests how two globally prevalent land uses - commercial agriculture and nature conservation - may influence social determinants of psychological distress in our study area. Psychological distress does not necessarily imply mental disorder. Nonetheless, exploring socially-mediated interactions with ecosystems may help explain the etiology of psychological distress. Furthermore, we suggest opportunities to manage socio-ecological systems to support mental health, such as promoting equitable access and control of livelihood resources. We also highlight co-benefits and trade-offs between global sustainability goals that could be managed for mental health, and why these should be recognized in the anticipated New Deal for Nature. HighlightsO_LIFood insecurity and poverty were major stressors reportedly causing psychological distress, characterized as "thinking too much." C_LIO_LIComplex interactions between conservation, commercial agriculture, and poverty influenced psychological distress. C_LIO_LICommercial agriculture displaced subsistence farming, exacerbating poverty and food security among poorer households. C_LIO_LIConserved forests were both home to crop-raiding wildlife and sources of income and food, affecting poverty and food insecurity. C_LIO_LIMental health needs to be included in assessments of the role of the ecosystems in public health. C_LI

ecology↗

bioRxiv2020

Modelling parameter uncertainty reveals bushmeat yield versus survival trade-offs in heavily-hunted duiker Cephalophus spp.

Reliably predicting sustainable exploitation levels for many tropical species subject to hunting remains a difficult task, largely because of the inherent uncertainty associated with estimating parameters related to both population dynamics and hunting pressure. Here, we investigate a modelling approach to support decisions in bushmeat management which explicitly considers parameter uncertainty. We apply the approach to duiker Cephalophus spp., assuming either a constant quota-based, or a constant proportional harvesting, strategy. Within each strategy, we evaluate different hunting levels in terms of both average yield and survival probability, over different time horizons. Under quota-based harvesting, considering uncertainty revealed a trade-off between yield and extinction probability that was not evident when ignoring uncertainty. The highest yield was returned by a quota that implied a 40% extinction risk, whereas limiting extinction risk to 10% reduced yield by 50%-70%. By contrast, under proportional harvesting, there was no trade-off between yield and extinction probability. The maximum proportion returned a yield comparable with the maximum possible under quota-based harvesting, but with extinction risk below 10%. However, proportional harvesting can be harder to implement in practice because it depends on an estimate of population size. In both harvesting approaches, predicted yields were highly right-skewed with median yields differing from mean yields, implying that decision outcomes depend on attitude to risk. The analysis shows how an explicit consideration of all available information, including uncertainty, can, as part of a wider process involving multiple stakeholders, help inform harvesting policies.

ecology↗

bioRxiv2020

Disconnects in global discourses - the unintended consequences of marine mammal protection on small-scale fishers

Globally, the populations of many marine mammals remain of critical concern after centuries of exploitation and hunting. However, some marine mammal populations (e.g. pinnipeds) have largely recovered from exploitation, and interactions between these species and fisheries--particularly small-scale fisheries--is once again of concern globally. The large scope and widespread scale of interactions highlights the local disconnect between two global policies: marine mammal conservation and small-scale fisheries protection. In this research, we explore these conflicting global policies by assessing the perceptions of coastal small-scale fishers in Peru and Chile regarding their interactions with pinnipeds, including the South American sea lion (Otaria flavescens) and South American fur seal (Arctocephalus australis). We surveyed 301 gill net fishers and assess perceptions using a best-worst scaling methodology. We find that fishers are chiefly concerned with the increase in pinniped populations, perceive that their interactions with pinnipeds have significantly increased over the past 80 years, and report pinniped-driven catch and income losses [≥] 26 per cent. Surprisingly, fishers do not believe that compensation schemes will resolve this issue--instead they overwhelmingly call for pinniped population culls. The reported number of pinnipeds illegally killed by fishers suggests the potential for large negative impacts on these protected species, and a loss of legitimacy in marine regulation. Collectively, our results portray a sense of marginalisation from fishers--that global policy treats them as less "important" than marine mammals. Our results highlight the increasing disconnect in global policy, which on one hand seeks to protect threatened marine mammal populations, and on the other seeks to promote the welfare of small-scale fishers.

ecology↗