This page contains a Flash digital edition of a book.
CO2


pH State and trends


Sea-level rise also affects natural communities such as salt marshes and mangroves at the edge of the water. These communities will have to migrate inland or increase their elevation in order to avoid being submerged by rising seas. As these are important habitats for birds and marine animals that use them as nursery habitats, many species are at risk if these wetlands cannot migrate. Coastal salt marshes and mangroves also serve as buffers, protecting human communities from storm surges and flooding. These wetlands provide many other benefits to humans, including habitat for commercially important fisheries and wildlife; improved water quality through sediment, nutrient, and pollution removal; recreation; and aesthetic values. These valuable ecosystems are highly vulnerable to the sea-level rise projected to occur during the next century as a result of global warming. In many areas, marshes are not expected to be able to increase their elevation fast enough to keep up with sea-level rise, but if storms transport new sediments into the marshes, they may be able to increase their elevation and persist for a longer time. In developed areas, there are roads, houses, etc. just landward of the marshes, which prevent them from migrating inland.


Ocean acidification


When carbon dioxide from fossil-fuel burning enters the atmosphere (see Energy in Section 2.9), about one-third of it dissolves in the ocean where it combines with water to form carbonic acid, which becomes bicarbonate ions and hydrogen ions, making the water more acidic (Figure 2.5.4). Since the industrial age began in the 19th century, the acidity of the oceans has increased by 0.1 pH unit, which represents a 30 per cent increase in acidity. The extent of ocean acidification varies naturally between seasons, from one year to the next, and among regions and locations. Winds and currents that carry water around the ocean create localized pathways and acidic patches. In addition, direct observations only go back 30 years. Nevertheless, if carbon dioxide emissions continue at the present rate, models project an average worldwide increase of 0.2-0.3 pH units by 2100, in addition to what has already happened, doubling the current ocean acidity. The current change is extremely fast, more than one pH unit


Figure 2.5.4: Rising CO2 pH of seawater


4 25 4 0 0 3 7 5 3 5 0 3 25 3 0 0 27 5 19 5 5 19 6 5 19 7 5 19 85 Year


A t m o s p h e r i c C O 2 S e aw at e r p C O 2


S e aw at e r p H


The graph shows the correlation between rising levels of carbon dioxide (CO2


) in the atmosphere at Mauna Loa with rising CO2 levels in the nearby


ocean at Station Aloha. As more CO2 accumulates in the ocean, the pH of the ocean decreases. Source: Adapted from Feely et al. 2009


to 200 years. While some marine organisms will be able to tolerate these conditions or evolve to tolerate them, changes may be too fast for many to adapt (Kroeker et al. 2010).


Ocean acidification threatens the ecological health of the oceans and the economic wellbeing of the people who depend on a healthy marine environment. It is expected to harm a wide range of ocean life, particularly those that use calcium and carbonate ions from seawater to produce calcium carbonate for their shells. Larval molluscs and some other calcifying organisms are already showing impaired shell formation at some locations, and calcareous plankton, including some phytoplankton at the base of oceanic food webs, corals and shellfish are threatened.


101 ( p p p m v ) ( at m ) 19 9 5 20 0 5 20 15


in atmosphere, CO2


in oceans, and


8.0 8 8.13 8.18 8.23 8.28 8.3 3


8.0 3


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164  |  Page 165  |  Page 166  |  Page 167  |  Page 168  |  Page 169  |  Page 170  |  Page 171  |  Page 172  |  Page 173  |  Page 174  |  Page 175  |  Page 176  |  Page 177  |  Page 178  |  Page 179  |  Page 180  |  Page 181  |  Page 182  |  Page 183  |  Page 184  |  Page 185  |  Page 186  |  Page 187  |  Page 188  |  Page 189  |  Page 190  |  Page 191  |  Page 192  |  Page 193  |  Page 194  |  Page 195  |  Page 196  |  Page 197  |  Page 198  |  Page 199  |  Page 200  |  Page 201  |  Page 202  |  Page 203  |  Page 204  |  Page 205  |  Page 206  |  Page 207  |  Page 208  |  Page 209  |  Page 210  |  Page 211  |  Page 212  |  Page 213  |  Page 214  |  Page 215  |  Page 216  |  Page 217  |  Page 218  |  Page 219  |  Page 220  |  Page 221  |  Page 222  |  Page 223  |  Page 224  |  Page 225  |  Page 226  |  Page 227  |  Page 228  |  Page 229  |  Page 230  |  Page 231  |  Page 232  |  Page 233  |  Page 234  |  Page 235  |  Page 236  |  Page 237  |  Page 238  |  Page 239  |  Page 240  |  Page 241  |  Page 242  |  Page 243  |  Page 244  |  Page 245  |  Page 246  |  Page 247  |  Page 248  |  Page 249  |  Page 250  |  Page 251  |  Page 252  |  Page 253  |  Page 254  |  Page 255  |  Page 256  |  Page 257  |  Page 258  |  Page 259  |  Page 260  |  Page 261  |  Page 262  |  Page 263  |  Page 264  |  Page 265  |  Page 266  |  Page 267  |  Page 268  |  Page 269  |  Page 270  |  Page 271  |  Page 272  |  Page 273  |  Page 274  |  Page 275  |  Page 276  |  Page 277  |  Page 278  |  Page 279  |  Page 280  |  Page 281  |  Page 282  |  Page 283  |  Page 284  |  Page 285  |  Page 286  |  Page 287  |  Page 288  |  Page 289  |  Page 290  |  Page 291  |  Page 292  |  Page 293  |  Page 294  |  Page 295  |  Page 296  |  Page 297  |  Page 298  |  Page 299  |  Page 300  |  Page 301  |  Page 302  |  Page 303  |  Page 304  |  Page 305  |  Page 306  |  Page 307  |  Page 308  |  Page 309  |  Page 310  |  Page 311  |  Page 312  |  Page 313  |  Page 314  |  Page 315  |  Page 316  |  Page 317  |  Page 318  |  Page 319  |  Page 320  |  Page 321  |  Page 322  |  Page 323  |  Page 324  |  Page 325