Elvira S. Poloczanska

The ‘Great Southern Reef’: social, ecological and economic value of Australia’s neglected kelp forests

Kelp forests define >8000km of temperate coastline across southern Australia, where ~70% of Australians live, work and recreate. Despite this, public and political awareness of the scale and significance of this marine ecosystem is low, and research investment miniscule (<10%), relative to comparable ecosystems. The absence of an identity for Australia’s temperate reefs as an entity has probably contributed to the current lack of appreciation of this system, which is at odds with its profound ecological, social and economic importance. We define the ‘Great Southern Reef’ (GSR) as Australia’s spatially connected temperate reef system. The GSR covers ~71000km2 and represents a global biodiversity hotspot across at least nine phyla. GSR-related fishing and tourism generates at least AU

Ecosystem-based adaptation in marine ecosystems of tropical Oceania in response to climate change

10 billion year–1, and in this context the GSR is a significant natural asset for Australia and globally. Maintaining the health and ecological functioning of the GSR is critical to the continued sustainability of human livelihoods and wellbeing derived from it. By recognising the GSR as an entity we seek to boost awareness, and take steps towards negotiating the difficult challenges the GSR faces in a future of unprecedented coastal population growth and global change.

Coral reef ecosystems under climate change and ocean acidification

Tropical Oceania, including Melanesia, Polynesia, Micronesia and northern Australia, is one of the most biodiverse regions of the world. Climate change impacts have already occurred in the region and will become one of the greatest threats to biodiversity and people. Climate projections indicate that sea levels will rise in many places but not uniformly. Islands will warm and annual rainfall will increase and exhibit strong decadal variations. Increases in global atmospheric CO2 concentration are causing ocean acidification, compromising the ability of organisms such as corals to maintain their calcium carbonate skeletons. We discuss these climate threats and their implications for the biodiversity of several ecosystems (coral reefs, seagrass and mangroves) in the region. We highlight current adaptation approaches designed to address these threats, including efforts to integrate ecosystem and community-based approaches. Finally, we identify guiding principles for developing effective ecosystem-based adaptation strategies. Despite broad differences in governance and social systems within the region, particularly between Australia and the rest of the Pacific, threats and planning objectives are similar. Ensuring community awareness and participation are essential everywhere. The science underpinning ecosystem-based adaptation strategies is in its infancy but there is great opportunity for communicating approaches and lessons learnt between developing and developed nations in tropical Oceania.

Ocean currents modify the coupling between climate change and biogeographical shifts

Coral reefs are found in a wide range of environments, where they provide food and habitat to a large range of organisms as well as other ecological goods and services. Warm-water coral reefs, for example, occupy shallow sunlit, warm and alkaline waters in order to grow and calcify at the high rates necessary to build and maintain their calcium carbonate structures. At deeper locations (40 – 150 m), “mesophotic” (low light) coral reefs accumulate calcium carbonate at much lower rates (if at all in some cases) yet remain important as habitat for a wide range of organisms, including those important for fisheries. Finally, even deeper, down to 2000 m or more, the so-called ‘cold-water’ coral reefs are found in the dark depths. Despite their importance, coral reefs are facing significant challenges from human activities including pollution, over-harvesting, physical destruction, and climate change. In the latter case, even lower greenhouse gas emission scenarios (such as Representative Concentration Pathway RCP 4.5) are likely drive the elimination of most warm-water coral reefs by 2040-2050. Cold-water corals are also threatened by warming temperatures and ocean acidification although evidence of the direct effect of climate change is less clear. Evidence that coral reefs can adapt at rates which are sufficient for them to keep up with rapid ocean warming and acidification is minimal, especially given that corals are long-lived and hence have slow rates of evolution. Conclusions that coral reefs will migrate to higher latitudes as they warm are equally unfounded, with the observations of tropical species appearing at high latitudes ‘necessary but not sufficient’ evidence that entire coral reef ecosystems are shifting. On the contrary, coral reefs are likely to degrade rapidly over the next 20 years, presenting fundamental challenges for the 500 million people who derive food, income, coastal protection, and a range of other services from coral reefs. Unless rapid advances to the goals of the Paris Climate Change Agreement occur over the next decade, hundreds of millions of people are likely to face increasing amounts of poverty and social disruption, and, in some cases, regional insecurity.

Climate Regulation as a Service from Estuarine and Coastal Ecosystems

Biogeographical shifts are a ubiquitous global response to climate change. However, observed shifts across taxa and geographical locations are highly variable and only partially attributable to climatic conditions. Such variable outcomes result from the interaction between local climatic changes and other abiotic and biotic factors operating across species ranges. Among them, external directional forces such as ocean and air currents influence the dispersal of nearly all marine and many terrestrial organisms. Here, using a global meta-dataset of observed range shifts of marine species, we show that incorporating directional agreement between flow and climate significantly increases the proportion of explained variance. We propose a simple metric that measures the degrees of directional agreement of ocean (or air) currents with thermal gradients and considers the effects of directional forces in predictions of climate-driven range shifts. Ocean flows are found to both facilitate and hinder shifts depending on their directional agreement with spatial gradients of temperature. Further, effects are shaped by the locations of shifts in the range (trailing, leading or centroid) and taxonomic identity of species. These results support the global effects of climatic changes on distribution shifts and stress the importance of framing climate expectations in reference to other non-climatic interacting factors.

Misconceptions about analyses of Australian seaweed collections

Coastal regions, at the interface between terrestrial and oceanic ecosystems, play an important role in global biogeochemical cycles. This chapter reviews the climate regulation services of estuarine and coastal ecosystems (ECEs) including tidal salt marshes, mangroves, seagrass beds, macroalgal forests, coral reefs, and coastal shelf ecosystems. ECEs regulate global and regional climates by sequestering or releasing carbon dioxide and other greenhouse gases (GHGs). ECEs are extremely productive biologically, with net primary production rates per unit area among the highest of any ecosystem. Consequently, ECEs play a globally significant role as carbon sinks, with carbon storage rates per unit area of many habitats far exceeding that of land habitats at the rate of about 10 times that of temperate terrestrial forests and 50 times that of tropical forests. Furthermore, sedimentation does not reach an equilibrium carbon balance as occurs in terrestrial systems, whose sequestration capacity is forecasted to decrease this century. Conversely, they are large potential sources of GHG’s if disturbed or mismanaged. Critically, carbon sequestration in many coastal habitats is superior to that of terrestrial habitats, as carbon is generally stored over long time frames (thousands of years) as a consequence of the large belowground biomass and the absence of fire threat. Furthermore, carbon is generally broken down anaerobically; hence, emissions of other potent GHGs such as methane and nitrous oxide are negligible. A review of literature provided sequestration rates for various coastal habitats. Using these in combination with global extent of selected habitats, this chapter finds that GHGs worldwide, mangroves, seagrass beds, and salt marshes combine to sequester a minimum of 136 000 tonnes C annually into long-term carbon storage. Assuming prices of CO2e from

Are fish outside their usual ranges early indicators of climate-driven range shifts?

10 to

Climate velocity can inform conservation in a warming world

90 per tonne, the value of the annual sequestration is

Improving the interpretability of climate landscape metrics: An ecological risk analysis of Japan's Marine Protected Areas

5 –45 billion. This is an underestimate due to data gaps and, the limited assessment of the area of these three coastal ecosystem habitats, and relates only to long-term storage. The figures do not include short-term carbon storage in biomass, and further unaccounted for carbon sequestration occurs in kelp forests, estuaries, and coastal shelf seas. Many ECEs are under threat globally from sea-level rise, coastal development, pollution, and other anthropogenic stressors, and protection and restoration of ECEs may be an important tool for mitigating climate change. Currently, these habitats are not included in the United Nations Framework Convention on Climate Change (UNFCCC) carbon accounting frameworks, and therefore are excluded from incentive schemes such as carbon markets and other incentive programs, but their inclusion deserves consideration due to their potential for mitigating global climate change. The global distribution of C sequestration in ECEs reveals that large areas of the tropics are home to the highest sequestration rates and occur in developing countries, which also have the highest rates of coastal habitat degradation. Schemes such as Reducing Emissions from Deforestation and Forest Degradation (REDD) may bring revenues and added benefits to developing countries for instigating projects and marine protected areas for conservation. Many small island nations and developing countries in the tropics are particularly vulnerable to climate change and contain large swathes of seagrasses and mangroves compared to overall land area, but do not contain large areas of forests or grasslands, which would apply to REDD in its current form. Coastal habitats thus not only present an untapped potential for inclusion in climate change mitigation schemes, but also present a little-recognized risk of loss of large carbon stocks if their degradation and destruction are not reduced or halted.

Keeping watch on the ocean

Abstract: One of the greatest impediments to detecting changes in species distributions in response to ocean warming is the lack of baseline data. In a recent article, we compared old (1940–1959) and new (1990–2009) herbarium records of Australian seaweeds and found a net southward shift in the latitude of northernmost collections of temperate species, implying a flora-wide poleward retreat over the past five decades. Huisman & Millar (2013) criticised our methods, contending that a comparison of herbarium records from different time periods cannot be used to infer changes in species distributions without field-based validation. However, our analysis compared the median position of extreme records of random species from random locations rather than focusing on particular species and their possible loss from specific sites. Hence, ground-truthing ‘extinctions’ are of limited value to the interpretation of our analysis. Moreover, subtidal ground-truthing over biogeographic scales is not logistically possible and even runs counter to entire disciplines (e.g. palaeontology, extinction biology and biogeography) that assess hypotheses of extinction and shifting distributions. Huisman & Millar also questioned the direction of biases in the data set. We show here that patterns of collection effort should have produced an apparent shift northward in the absence of a true shift southward. Even if herbaria were not designed for the purpose of detecting species’ range changes, we contend that such collections can contain useful information on the distribution of species across space and time.