79
Long-Term Climate and Development Futures
Section 3
long-term planning and implementation of adaptation actions with 
beneﬁts to many sectors and systems. (high conﬁdence) {WGII SPM C.4, 
WGII SPM.C.4.1, WGII SPM C.4.2, WGII SPM C.4.3}
Sea level rise poses a distinctive and severe adaptation challenge 
as it implies both dealing with slow onset changes and increases 
in the frequency and magnitude of extreme sea level events (high 
conﬁdence). Such adaptation challenges would occur much earlier 
under high rates of sea level rise (high conﬁdence). Responses to ongoing 
sea level rise and land subsidence include protection, accommodation, 
advance and planned relocation (high conﬁdence). These responses 
are more effective if combined and/or sequenced, planned well ahead, 
aligned with sociocultural values and underpinned by inclusive 
community engagement processes (high conﬁdence). Ecosystem-based 
solutions such as wetlands provide co-beneﬁts for the environment 
and climate mitigation, and reduce costs for ﬂood defences (medium 
conﬁdence), but have site-speciﬁc physical limits, at least above 1.5ºC 
of global warming (high conﬁdence) and lose effectiveness at high 
rates of sea level rise beyond 0.5 to 1 cm yr-1 (medium conﬁdence). 
Seawalls can be maladaptive as they effectively reduce impacts in the 
short term but can also result in lock-ins and increase exposure to climate 
risks in the long term unless they are integrated into a long-term adaptive 
plan (high conﬁdence). {WGI SPM C.2.5; WGII SPM C.2.8, WGII SPM C.4.1; 
WGII 13.10, WGII Cross-Chapter Box SLR; SROCC SPM B.9, SROCC SPM C.3.2, 
SROCC Figure SPM.4, SROCC Figure SPM.5c} (Figure 3.4)