Search

Anthropogenic and natural disturbances can cause degradation of ecosystems, reducing their capacity to sustain biodiversity and provide ecosystem services. Understanding the extent of ecosystem degradation is critical for estimating risks to ecosystems, yet there are few existing methods to map degradation at the ecosystem scale and none using freely available satellite data for mangrove ecosystems. In this study, we developed a quantitative classification model of mangrove ecosystem degradation using freely available earth observation data. Crucially, a conceptual model of mangrove ecosystem degradation was established to identify suitable remote sensing variables that support the quantitative classification model, bridging the gap between satellite-derived variables and ecosystem degradation with explicit ecological links. We applied our degradation model to two case-studies, the mangroves of Rakhine State, Myanmar, which are severely threatened by anthropogenic disturbances, and Shark River within the Everglades National Park, USA, which is periodically disturbed by severe tropical storms. Our model suggested that 40% (597 km2) of the extent of mangroves in Rakhine showed evidence of degradation. In the Everglades, the model suggested that the extent of degraded mangrove forest increased from 5.1% to 97.4% following the Category 4 Hurricane Irma in 2017. Quantitative accuracy assessments indicated the model achieved overall accuracies of 77.6% and 79.1% for the Rakhine and the Everglades, respectively. We highlight that using an ecological conceptual model as the basis for building quantitative classification models to estimate the extent of ecosystem degradation ensures the ecological relevance of the classification models. Our developed method enables researchers to move beyond only mapping ecosystem distribution to condition and degradation as well. These results can help support ecosystem risk assessments, natural capital accounting, and restoration planning and provide quantitative estimates of ecosystem degradation for new global biodiversity targets.

Accurately evaluating ecosystem status is vital for effective conservation. The Red List of Ecosystems (RLE) from the International Union for the Conservation of Nature (IUCN) is the global standard for assessing the risk of ecosystem collapse. Such tools are particularly needed for large, dynamic ecosystem complexes, such as the Indian Sundarbans mangrove forest. This ecosystem supports unique biodiversity and the livelihoods of millions, but like many mangrove forests around the world is facing substantial pressure from a range of human activities. Holistic, standardised and quantitative environment risk assessment frameworks are essential here, because previous assessments have either been qualitative in nature, or have generally considered single threats in isolation. We review these threats and utilise the RLE framework to quantitatively assess the risk of ecosystem collapse. Historical clearing and diminishing fish populations drove a status of Endangered (range: Vulnerable to Endangered), and ongoing threats including climate change and reduced freshwater supply may further impact this ecosystem. However, considering recent change, the outlook is more optimistic. Mangrove extent has stabilised, and analysis of mangrove condition highlights that only a small proportion of the forest is degraded. Using the RLE provides an authoritative avenue for further protection and recognition of the issues facing this UNESCO World Heritage Site. We also identify knowledge and data gaps in the Sundarbans that are likely common to coastal systems globally. By articulating these and presenting opportunities and recommendations, we aim to further the conservation goals of the IUCN and the implementation of its new assessment framework.

Conservation science is a crisis-oriented discipline focused on delivering robust answers to reducing human impacts on nature. To explore how the field might have changed during the past two decades, we analyzed 3,245 applications for oral presentations submitted to the Student Conference on Conservation Science (SCCS) in Cambridge, UK. SCCS has been running every year since 2000, aims for global representation by providing bursaries to early-career conservationists from lower-income countries, and has never had a thematic focus, beyond conservation in the broadest sense. We found that the majority of submissions to SCCS were based on primary biological data collection from local scale field studies in the tropics, contrary to established literature which highlights gaps in tropical research. Our results showed a small increase over time in submissions framed around how nature benefits people as well as a small increase in submissions integrating social science. Our findings also suggest that students and early-career conservationists could provide pathways to increased availability of data from the tropics and for addressing well-known biases in the published literature towards wealthier countries. We hope this research will motivate efforts to support student projects, ensuring data and results are published and made publicly available.

Decreases in the abundance and diversity of stream fishes in the North American Great Plains have been attributed to habitat fragmentation, altered hydrological and temperature regimes, and elevated levels of total dissolved solids and total suspended solids. Pelagic-broadcast spawning cyprinids, such as the Arkansas River Shiner Notropis girardi, may be particularly vulnerable to these changing conditions because of their reproductive strategy. Our objectives were to assess the effects of temperature, total dissolved solids, and total suspended solids on the developmental and survival rates of Arkansas River Shiner larvae. Results suggest temperature had the greatest influence on the developmental rate of Arkansas River Shiner larvae. However, embryos exposed to the higher levels of total dissolved solids and total suspended solids reached developmental stages earlier than counterparts at equivalent temperatures. Although this rapid development may be beneficial in fragmented waters, our data suggest it may be associated with lower survival rates. Furthermore, those embryos incubating at high temperatures, or in high levels of total dissolved solids and total suspended solids resulted in less viable embryos and larvae than those incubating in all other temperature, total dissolved solid, and total suspended solid treatment groups. As the Great Plains ecoregion continues to change, these results may assist in understanding reasons for past extirpations and future extirpation threats as well as predict stream reaches capable of sustaining Arkansas River Shiners and other species with similar early life-history strategies.

Amphibian metamorphosis is complex and larval morphology and physiology are completely restructured during this time. Amphibians that live in unpredictable environments are often exposed to stressors that can directly and indirectly alter physiological systems during development, with subsequent consequences (carryover effects) later in life. In this study, we investigated the effects of water level reduction on development rate, spleen size and cellularity, and examined the role of corticosterone levels in premetamorphic, metamorphic, and postmetamorphic New Mexico spadefoot toads (Spea multiplicata). Based on previous studies, we hypothesized that declining water level would increase tadpole developmental rate, but with the trade-off of increasing corticosterone to a level that would subsequently affect spleen size and cellularity, thus prolonging potential immunological suppression. Declining water levels increased developmental rate by 3 days; however, there were no significant body size effects. Corticosterone (CORT) was negatively correlated with total length, snout vent length, body weight, and spleen weight at metamorphosis, suggesting that size at metamorphosis and the immune system may be affected by excessive CORT levels. When compared to other studies, our results support the view that multiple factors may be acting as stressors in the field affecting amphibian responses, and simple pathways as tested in this study may not adequately represent field conditions.