Editing IPCC:AR6/SR15/Chapter-3 (section)

==== 3.4.5.7 Adapting to coastal change ====

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Adaptation to coastal change from SLR and other drivers is occurring today ( ''high confidence'' ) (see Cross-Chapter Box 9 in Chapter 4), including migration, ecosystem-based adaptation, raising infrastructure and defences, salt-tolerant food production, early warning systems, insurance and education (Section 5.4.2.1 of Wong et al., 2014) <sup>[[#fn:r810|810]]</sup> . Climate change mitigation will reduce the rate of SLR this century, decreasing the need for extensive and, in places, immediate adaptation. Adaptation will reduce impacts in human settings ( ''high confidence'' ) (Hinkel et al., 2014; Wong et al., 2014) <sup>[[#fn:r811|811]]</sup> , although there is less certainty for natural ecosystems (Sections 4.3.2 and 4.3.3.3). While some ecosystems (e.g., mangroves) may be able to move shoreward as sea levels increase, coastal development (e.g., coastal building, seawalls and agriculture) often interrupt these transitions (Saunders et al., 2014) <sup>[[#fn:r812|812]]</sup> . Options for responding to these challenges include reducing the impact of other stresses such as those arising from tourism, fishing, coastal development and unsustainable aquaculture/agriculture. In some cases, restoration of coastal habitats and ecosystems can be a cost-effective way of responding to changes arising from increasing levels of exposure from rising sea levels, changes in storm conditions, coastal inundation and salinization (Arkema et al., 2013; Temmerman et al., 2013; Ferrario et al., 2014; Hinkel et al., 2014; Spalding et al., 2014; Elliff and Silva, 2017) <sup>[[#fn:r813|813]]</sup> .

Since AR5, planned and autonomous adaptation and forward planning have become more widespread (Araos et al., 2016; Nicholls et al., 2018) <sup>[[#fn:r814|814]]</sup> , but continued efforts are required as many localities are in the early stages of adapting or are not adapting at all (Cross-Chapter Box 9 in Chapter 4; Araos et al., 2016) <sup>[[#fn:r815|815]]</sup> . This is region and sub-sector specific, and also linked to non-climatic factors (Ford et al., 2015; Araos et al., 2016; Lesnikowski et al., 2016) <sup>[[#fn:r816|816]]</sup> . Adaptation pathways (e.g., Ranger et al., 2013; Barnett et al., 2014; Rosenzweig and Solecki, 2014; Buurman and Babovic, 2016) <sup>[[#fn:r817|817]]</sup> assist long-term planning but are not widespread practices despite knowledge of long-term risks (Section 4.2.2). Furthermore, human retreat and migration are increasingly being considered as an adaptation response (Hauer et al., 2016; Geisler and Currens, 2017) <sup>[[#fn:r818|818]]</sup> , with a growing emphasis on green adaptation. There are few studies on the adaptation limits to SLR where transformation change may be required (AR5 Section 5.5 of Wong et al., 2014 <sup>[[#fn:r819|819]]</sup> ; Nicholls et al., 2015 <sup>[[#fn:r820|820]]</sup> ). Sea level rise poses a long-term threat (Section 3.3.9), and adaptation will remain essential at the centennial scale under 1.5°C and 2°C of warming ( ''high confidence'' ).

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'''Table 3.3'''

<span id="land-and-people-exposed-to-sea-level-rise-slr-assuming-no-protection-at-all.-extracted-from-brown-et-al.-2018a-and-goodwin-et-al.-2018.-ssp-shared-socio--economic-pathway-wrt-with-respect-to-population-held-constant-at-2100-level."></span>
'''Land and people exposed to sea level rise (SLR), assuming no protection at all. Extracted from Brown et al. (2018a) and Goodwin et al. (2018). SSP: Shared Socio- Economic Pathway; wrt: with respect to; *: Population held constant at 2100 level.'''

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{| class="wikitable"
|-
! rowspan="2"| Climate scenario
! rowspan="2"| Impact factor, assuming there is no adaptation or protection at all (50th, [5th-95th percentiles])
! colspan="4"| Year
|-
! 2050
! 2100
! 2200
! 2300
|-
| 1.5°C
| Temperature rise wrt 1850–1900 (°C)
| 1.71
(1.44–2.16)

| 1.60
(1.26–2.33)

| 1.41
(1.15–2.10)

| 1.32
(1.12–1.81)

|-
|
| SLR (m) wrt 1986–2005
| 0.20
(0.14–0.29)

| 0.40
(0.26–0.62)

| 0.73
(0.47–1.25)

| 1.00
(0.59–1.55)

|-
|
| Land exposed (x10 <sup>3</sup> km <sup>2</sup> )
| 574
[558–597]

| 620
[575–669]

| 666
[595–772]

| 702
[666–853]

|-
|
| People exposed, SSP1–5 (millions)
| 127.9–139.0
[123.4–134.0,<br />
134.5–146.4]

| 102.7–153.5
[94.8–140.7,<br />
102.7–153.5]

| —
| 133.8–207.1
[112.3–169.6, 165.2–263.4]*

|-
| 2°C
| Temperature rise wrt 1850–1900 (° C)
| 1.76
(1.51–2.16)

| 2.03
(1.72–2.64)

| 1.90
(1.66–2.57)

| 1.80
(1.60–2.20)

|-
|
| SLR (m) wrt 1986-2005

| 0.20
(0.14–0.29)

| 0.46
(0.30–0.69)

| 0.90
(0.58–1.50)

| 1.26
(0.74–1.90)

|-
|
| Land exposed (x10 <sup>3</sup> km <sup>2</sup> )

| 575
[558–598]

| 637
[585–686]

| 705
[618–827]

| 767
[642–937]

|-
|
| People exposed, SSP1–5 (millions)

| 128.1–139.2
[123.6–134.2,<br />
134.7–146.6]

| 105.5–158.1
[97.0–144.1,<br />
118.1–179.0]

| —
| 148.3–233.0
[120.3–183.4, 186.4–301.8]*

|}
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