Sea ice in the Arctic is one of the most rapidly changing components of the global climate system. Over the past few decades, summer areal extent has declined over 30, and all months show statistically significant declining trends. New satellite missions and techniques have greatly expanded information on sea ice thickness, but many uncertainties remain in the satellite data and long-term records are sparse. However, thickness observations and other satellite-derived data indicate a 40 decline in thickness, due in large part to the loss of thicker, older ice cover. The changes in sea ice are happening faster than models have projected. With continued increasing temperatures, summer ice-free conditions are likely sometime in the coming decades, though there are substantial uncertainties in the exact timing and high interannual variability will remain as sea ice decreases. The changes in Arctic sea ice are already having an impact on flora and fauna in the Arctic. Some species will face increasing challenges in the future, while new habitat will open up for other species. The changes are also affecting peoples living and working in the Arctic. Native communities are facing challenges to their traditional ways of life, while new opportunities open for shipping, fishing, and natural resource extraction.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2013RG000431

Arctic sea ice in transformation: A review of recent observed changes and impacts on biology and human activity

Arctic marine mammals (AMMs) are icons of climate change, largely because of their close association with sea ice However, neither a circumpolar assessment of AMM status nor a standardized metric of sea ice habitat change is available We summarized available data on abundance and trend for each AMM species and recognized subpopulation We also examined species diversity, the extent of human use, and temporal trends in sea ice habitat for 12 regions of the Arctic by calculating the dates of spring sea ice retreat and fall sea ice advance from satellite data (1979–2013) Estimates of AMM abundance varied greatly in quality, and few studies were long enough for trend analysis Of the AMM subpopulations, 78% (61 of 78) are legally harvested for subsistence purposes Changes in sea ice phenology have been profound In all regions except the Bering Sea, the duration of the summer (ie, reduced ice) period increased by 5–10 weeks and by >20 weeks in the Barents Sea between 1979 and 2013 In light of generally poor data, the importance of human use, and forecasted environmental changes in the 21st century, we recommend the following for effective AMM conservation: maintain and improve comanagement by local, federal, and international partners; recognize spatial and temporal variability in AMM subpopulation response to climate change; implement monitoring programs with clear goals; mitigate cumulative impacts of increased human activity; and recognize the limits of current protected species legislation

https://onlinelibrary.wiley.com/doi/pdf/10.1111/cobi.12474

Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century.

Since the 1970s the role of fishery bycatch as a factor reducing, or limiting the recov- ery of, marine mammal populations has been increasingly recognized. The proceedings of a 1990 International Whaling Commission symposium and workshop summarized fishery and bycatch data by region, fishery, and species, and estimated the significance of the 'impacts' of bycatch in passive gear on all cetacean species and subspecies or geographically defined populations. A global review of pinniped bycatch in 1991 concluded that incidental mortality in passive gear had contributed to declines of several species and populations. Here we update the information on cetacean gillnet bycatch, assess bycatch data on marine mammals other than cetaceans (i.e. pin- nipeds, sirenians, and 2 otter species), determine where important data gaps exist, and identify species and populations known or likely to be at high risk from bycatch in gillnets. We found that at least 75% of odontocete species, 64% of mysticetes, 66% of pinnipeds, and all sirenians and marine mustelids have been recorded as gillnet bycatch over the past 20-plus years. Cetacean bycatch information in some areas has improved, facilitating our ability to identify species and populations at high risk, although major gaps remain. Understanding of the scale of pinniped and sirenian bycatch has also improved, but this bycatch remains poorly documented, especially at the population level. This study reveals how little is known about marine mammal bycatch in gillnets in much of the world. Even as other significant threats to marine mammals have become better documented and understood, bycatch remains a critical issue demanding urgent attention if there is to be any hope of preventing further losses of marine mammal diversity and abundance, and of protecting, or restoring, ecological health.

/pdf/marine-mammal-bycatch-in-gillnet-and-other-entangling-net-4hrqkyh7v8.pdf

Marine mammal bycatch in gillnet and other entangling net fisheries, 1990 to 2011

Stressors associated with human activities interact in complex ways to affect marine ecosystems, yet we lack spatially explicit assessments of cumulative impacts on ecologically and economically key components such as marine predators. Here we develop a metric of cumulative utilization and impact (CUI) on marine predators by combining electronic tracking data of eight protected predator species (n ¼ 685 individuals) in the California Current Ecosystem with data on 24 anthropogenic stressors. We show significant variation in CUI with some of the highest impacts within US National Marine Sanctuaries. High variation in underlying species and cumulative impact distributions means that neither alone is sufficient for effective spatial management. Instead, comprehensive management approaches accounting for both cumulative human impacts and trade-offs among multiple stressors must be applied in planning the use of marine resources.

/pdf/cumulative-human-impacts-on-marine-predators-4m9jsbihxo.pdf

Cumulative human impacts on marine predators

A quantitative assessment of observed and projected environmental changes in the Southern Ocean (SO) with a potential impact on the marine ecosystem shows: (i) large proportions of the SO are and will be affected by one or more climate change processes; areas projected to be affected in the future are larger than areas that are already under environmental stress, (ii) areas affected by changes in sea-ice in the past and likely in the future are much larger than areas affected by ocean warming. The smallest areas (<1% area of the SO) are affected by glacier retreat and warming in the deeper euphotic layer. In the future, decrease in the sea-ice is expected to be widespread. Changes in iceberg impact resulting from further collapse of ice-shelves can potentially affect large parts of shelf and ephemerally in the off-shore regions. However, aragonite undersaturation (acidification) might become one of the biggest problems for the Antarctic marine ecosystem by affecting almost the entire SO. Direct and indirect impacts of various environmental changes to the three major habitats, sea-ice, pelagic and benthos and their biota are complex. The areas affected by environmental stressors range from 33% of the SO for a single stressor, 11% for two and 2% for three, to <1% for four and five overlapping factors. In the future, areas expected to be affected by 2 and 3 overlapping factors are equally large, including potential iceberg changes, and together cover almost 86% of the SO ecosystem.

/pdf/the-southern-ocean-ecosystem-under-multiple-climate-change-2dmq8gr07e.pdf

The Southern Ocean Ecosystem Under Multiple Climate Change Stresses - An Integrated Circumpolar Assessment

The 2008 IUCN (International Union for Conservation of Nature) review of the status of the world’s mammals identified marine mammals (IUCN 2008) as disproportionally threatened and data poor compared to their terrestrial counterparts, and their status was noted as a particular concern (IUCN 2008, Mace et al. 2008, Schipper et al. 2008). The threats faced by marine mammals were identified as being different, with accidental mortality and pollution being dominant threats that superseded habitat loss, which was identified as the principal concern for land mammals. It was suggested that harvesting remained a major threat for half of the marine mammal species in the world. The distribution of marine mammals was described as being concentrated in tropical and temperate coastal platforms and associated with high levels of primary productivity. Threat levels were highest for marine mammals living in the North Atlantic, North Pacific and Southeast Asia. Range size was described as generally declining toward both poles. Although these generalities are of course correct for all marine mammals, it must be recognized that the larger number of species of cetaceans compared to other marine mammal groups (85 cetaceans, the polar bear Ursus maritimus, 4 extant sirenians and 36 pinniped species) biases the conclusions in the assessment for marine mammals to such a degree that a separate summary for the pinnipeds of the world is warranted. Additionally, a species-level assessment masks some important conservation concerns for pinnipeds with species classified as Least Concern actually containing threatened subspecies ( e.g., ringed seals). Finally, and perhaps most importantly, climate change issues were not specifically addressed in the vast majority of marine mammal assessments done for the 2008 IUCN review (IUCN 2008). We present here a complete assessment of the status and threats facing pinnipeds at the subspecies level, integrating the expected impacts of changing patterns of threat due to global climate change.

https://repositoriodigital.ipn.mx/bitstream/123456789/12836/1/kovacs_kit_m._2012_marine_mammal_science_3750.pdf

Tero Sipilä

Papers

Global threats to pinnipeds