A TOLL ON ATOLLS
The biggest threat to the worlds atolls is from human induced global warming causing extreme climate changes (CC), sea level rise (SLR) and ocean acidification. Darwin worked out that atolls formed on top of volcanoes and thought that they subsided and left atolls and today we also consider that erosion is a key contributor to the underlying volcanoes demise. However, subsidence or erosion generally takes place on a longer time frame than accelerating climate change; other than a major earthquake generated subsidence event and resulting tsunami.
What can atoll island populations do to preserve and extend their thousand year occupations in light of CC? Current ecological disaster risk reduction or natural re-engineering may be the answer! What is the basis for these programs? It is the understanding that critical basic human needs are also the focus of protecting or building resilience e.g. providing safety, protecting water and food production.
Other than water tanks, the most important source of water is groundwater. It has been known for a century, using the ghyben-hertzberg equation that a permeable (hydraulicly conductive) unconfined aquifer such as coral atolls can form a lens of fresh water above (asl) and below sea level (bsl) due to salinity differences e.g. for every 1m asl (only possible if atoll 1km wide) there is up to 40m bsl.
However, SLR and storm surges from tropical cyclones will impact fresh water. Protecting groundwater also means managing contaminants from humans i.e. faecal coliforms, by way of properly constructed wetlands (impermeable base using cheap bentonite). The solution to pollution by dilution within the expanse of surrounding ocean may be convenient but could also be detrimental e.g. build-up of harmful algal blooms within lagoons that are not flushed regularly. Managing ‘solid wastes’ through wetlands may provide not only a natural water recycling system, fill for building up land elsewhere and fertilised soil, dependent on using biodegradable and non-contaminated wastes (‘anti’ biotics, herbicides and poisonous ‘sterilising’ cleaners).
The idea of raised garden beds is not new either, while creating wetlands (cut and fill) new, elevated beds can be established that are easier to use, especially as the population becomes older with the younger generation leaving for education and work opportunities elsewhere. Planting more saline resistant trees e.g. replanting mangroves areas to protect shorelines and trees such as Chinchilla White Gum to provide timber. A disbursed number of Pacific nurseries could be established under SPREP (HQ in Tonga) to provide more resilient and varied food sources.
Wealthy travellers pay a premium to visit the beautiful coral reefs of the world such as those stretching from Lord Howe Island to Lord Howe Atoll (Ontong Java is one of the world’s largest atolls built on the world’s largest geologically ‘recent’ volcanic eruptions) and beyond, could be asked to contribute to a dedicated A TOLL FUND to help low lying and vulnerable communities become more resilient.
Due to arctic melt SLR, all low lying (below 5m asl) land will be abandoned unless we can somehow halt and reverse the inevitable tides and flooding. Security requires a major shift in tribal villages way of constructing safe places to live and may be cost prohibitive without donor funding. Providing a central disaster resilient village shelter is paramount to long-term safety other than temporarily relocating whole populations prior to TCs. The construction of new villages within a raised platform requires the abandonment and relocation of land that may require the breaking down of old linear hierarchies for the long-term survival of the tribe. This requires the realisation and acceptance that new ways of surviving require new ways of living and leadership for the rest of the world!