In the context of small islands and low-lying areas, the
or human-built barriers it will be difficult for these plant
following discussion identifies some of the sectors, sys-
and animal communities to survive as sea level rises.
tems and localities that are especially vulnerable to sea-
Moreover, impacts on one or more ‘leverage species’ can
level rise. Vulnerability is influenced not only by the na-
result in sweeping community-level changes
59
.
ture of the impacts, but also by the capacity to adapt.
Vulnerability of sediment processes and
Vulnerability of coastal wetlands, mangroves
coastal zones
and biodiversity
Accelerated sea-level rise will exacerbate the problems
Since coastal vegetated wetlands are intimately linked
of coastal erosion which are already widespread globally.
to sea level, these ecosystems are sensitive to long-term
But there is not a simple relationship between sea-level
sea-level change. Modelling of coastal wetlands (exclud-
rise and the retreat of low-lying coasts
60
. For example,
ing sea grasses) suggests that 33 per cent of global wet-
large amounts of sand from the neighbouring open
lands would be lost with a 36 cm rise in sea level from
coast can be transported into estuaries and lagoons due
2000 to 2080 and 44 per cent would be lost with a 72 cm
to sea level rise. As a result, local erosion rates for these
rise in sea level over this period
55
. Losses would be most
coasts can be an order of magnitude greater than simple
severe on the Atlantic and Gulf of Mexico coasts of North
equilibrium models would suggest
61
.
and Central America, the Caribbean, the Mediterranean,
the Baltic and most small island regions, largely reflect-
Changes in sediment supply can influence atoll island
ing their low tidal range.
morphology to at least the same extent as sea-level rise
62,63
.
This is consistent with the view that uninhabited islands
A global assessment of mangrove accretion rates
56
indi-
of the Maldives are morphologically resilient while those
cates that the rate at which mangroves grow in height is
that have been subject to substantial human modifica-
variable but commonly approaches 5 mm per year. This
tion (Figure 6C.9) are inherently more vulnerable
64,65
.
is greater than recent, and even many projected, rates of
increase in global mean sea level. However, many man-
Vulnerability of coral reefs
grove shorelines are subsiding and thus experiencing a
more rapid relative sea-level rise
57
. Sea-level rise could
Healthy coral reefs have kept pace with rapid postglacial
reduce the current half-million hectares of mangroves
sea-level rise, suggesting that the projected rates of sea-
in 16 Pacific Island countries and territories by as much
level rise are unlikely to threaten these reef ecosystems,
as 13 per cent by 2100
58
.
at least over the next few decades
66
. Some Indo-Pacific
reef flats are currently exposed at low tide. Anticipated
Higher relative coastal water levels, and the associated
increases in sea level might well result in their submer-
increasing salinity of estuarine systems, will encourage
gence and subsequent recolonization by corals
67
. How-
the inland migration of coastal plant and animal commu-
ever, other climate stresses, especially rising sea surface
nities. However, if such migration is blocked by natural
temperature threaten many coral reefs worldwide
46
.
168 GLOBAL OUTLOOK FOR ICE AND SNOW
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