In Dead Water: Merging of climate change with - UNEP

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C M Y CM MY CY CMY K Africa Australia Europe Latin America North America Asia Global (total) 6c_onem_exposed.pdf 2007-05-22 17:25 Land area (thousand km 2 ) Population (millions) GDP (US$ billion) 0 200 400 600 800 0 25 50 75 100 0 100 200 300 400 2 223 000 km 2 145 millions US$944 billion Figure 16. Land area, number of people impacted and projected economic losses from a 1 metre uniform sea level rise in different regions (Anthoff et al., 2006; UNEP, 2007).
OCEAN ACIDIFICATION The oceans act as a natural reservoir for CO 2. The dissolved CO 2 reacts with the seawater to form hydrogen ions. The uptake of anthropogenic carbon since 1750 has led to the ocean becoming more acidic, with an average decrease in pH of 0.1 units. However, the effects of observed ocean acidification on the marine biosphere are yet mostly undocumented. Progressive acidification of the oceans due to increasing atmospheric carbon dioxide is expected to reduce biocalcification of the shells, bones and skeletons most marine organisms possess. Though the limited number of studies available makes it difficult to assess confidence levels, potentially severe ecological changes would result from ocean acidification, especially for corals both in tropical and cold water, and may influence marine food chains from carbonate-based plankton up to higher trophic levels. The oceans are naturally alkaline, with an average pH of around 8.2, although this can vary up to 0.3 units depending on location and season. Atmospheric carbon dioxide dissolves naturally in the ocean, forming carbonic acid (H 2CO 3), a weak acid. The hydrogen ions released from this acid lower the pH. These reactions are part of a natural buffer system, but recent studies have shown that the huge amounts of CO 2 created by burning fossil fuels are over-stretching the rate by which the natural process can neutralise this acidity. The pH of the oceans has decreased 0.1 unit compared to pre-industrial levels, which equals an increase of 30 per cent in hydrogen ions. While records show that the pH of the seas can vary slightly over time and in certain areas, the continued increases in atmospheric CO 2 are expected to alter ocean pH values within a very short time – an effect greater than any experienced in the past 300 million years (Caldeira et al., 2003).
Page 1 and 2: RAPID RESPONSE ASSESSMENT IN DEAD W
Page 3 and 4: Christian Nellemann Stefan Hain Jac
Page 5: PREFACE The world’s oceans are al
Page 8 and 9: covered and possible loss of cold-w
Page 10: Over-harvesting and bottom trawling
Page 13 and 14: CONTENTS 0 0 PREFACE SUMMARY WHY OC
Page 16 and 17: THE SEA - ONE OF THE LARGEST FOOD F
Page 18 and 19: SEAMOUNTS AND CONTINENTAL SHELVES -
Page 20 and 21: These unique features make seamount
Page 22 and 23: CORAL REEFS Coral reefs are marine
Page 25 and 26: More and more coral reefs are being
Page 27 and 28: CLIMATE CHANGE IN THE SEA The Fourt
Page 29 and 30: global bleaching event was recorded
Page 31 and 32: Number of events per year 450 400 3
Page 33: Figure 15. How sea level rise will
Page 37 and 38: Figure 18. As carbon concentrations
Page 39 and 40: SLOWING DOWN OF THERMOHALINE CIRCUL
Page 41 and 42: opean Seas) - of which UNEP is a pa
Page 43 and 44: Figure 23. Infrastructure developme
Page 45 and 46: Figure 24. Sewage treatment is low
Page 47: Among the most destructive fishing
Page 51 and 52: It is important, however, to realiz
Page 53 and 54: Figure 27. The locations of major p
Page 55 and 56: UNEP-WCMC & UNEP/GRID-Arendal Figur
Page 57 and 58: Overharvest from fisheries Coastal
Page 59 and 60: CONTRIBUTORS AND REVIEWERS Christia
Page 61 and 62: current status and prospects of ant
Page 64: UNEP/GRID-Arendal Teaterplassen 3 N

In Dead Water: Merging of climate change with - UNEP

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