Stimulus details: increased rainfall and flooding

impact chain for tropical coastal areas / increased rainfall and flooding (click nodes to view details):
Decreases or increases in rainfall and associated extreme events (e.g., drought, flooding) will affect coastal areas in different ways (see also the impact chain for decreased rainfall and drought). In mangrove ecosystems, drought could lead to increased salinity, which in turn results in growth decline, altered competition between species and the conversion of upper tidal zones to hypersaline flats.[13] In coastal settlements, major crop losses can be expected under drought because of the lack of fresh water for irrigation, especially in small islands. Such events have already weakened food security in the South Pacific Islands.[14]

On the other hand, increases in rainfall (both in coastal areas and in upland areas) will have an impact not only on coastal communities and wetlands, but also on coral reefs. Inland flooding can cause sediment discharge into coral reefs, which can be detrimental to their health.[15] Prolonged rainfall and flooding can also cause freshwater-induced bleaching, especially in reefs located further from the open ocean (e. g., in lagoons).[16]

Localised coastal flooding and inland/riverine flooding both have impacts on downstream coastal communities, as such events lead to the mass transportation of sediments and pollutants, and cause direct physical damage to settlements and agriculture.[14, 17] Limiting pollution and sediment discharge is the first step towards reducing ecosystem and community vulnerability.

Although extreme floods can have adverse impacts on mangroves, moderate increases in rainfall can be beneficial for coastal wetlands. To minimise any negative impacts from changes in rainfall and enhance any potential positive effects, sustainable management at the broader watershed level is needed.


[13]    Gilman, E. L., Ellison, J., Duke, N. C., Field, C., 2008. Threats to mangroves from climate change and adaptation options: a review. Aquatic Botany 89, 237-250.

[14]    Barnett, J., 2011. Dangerous climate change in the Pacific Islands: food production and food security. Regional Environmental Change 11, 229-237.

[15]    Pereira, M. A., Gonçalves, P. M. B., 2004. Effects of the 2000 southern Mozambique floods on a marginal coral community: the case at Xai-Xai. African Journal of Aquatic Science 29, 113-116.

[16]    Perry, C. T., 2003. Reef development at Inhaca Island, Mozambique: coral communities and impacts of the 1999/2000 southern African floods. AMBIO: A Journal of the Human Environment 32, 134-139.

[17]    Martínez Arroyo, A., Manzanilla Naim, S., Zavala Hidalgo, J., 2011. Vulnerability to climate change of marine and coastal fisheries in México. Atmósfera 24, 103-123.
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