On the Coromandel Peninsula, our Council – like many other coastal local authorities in New Zealand – have spent many millions of dollars on “hard” shoreline protection measures such as seawalls. Locally, this is particularly the case in and around Mercury Bay, and at the Thames suburb of Moanataiari. Large sums have also been spent already on “soft” erosion protection measures such as dune planting.
Over short time frames, it could be argued this is a sensible use of public money. But new research is suggesting that over longer time frames of many decades these measures will prove to be ineffective, have negative adverse consequences, and many people who live near coastlines will still likely have to relocate as seas continue to rise.
The research is suggesting that short-term adaptation options like sea walls can, in fact, increase the threat to public safety and property. This is because these actions temporarily raise the value of coastal property and in doing so discourage people from moving away from the coast.
These “hard” protection measures result in unintended consequences because they reduce incentives for communities to make long-term plans for retreating from the shore. They give a signal to individuals and businesses that the risks of living near the coast are lower and encourages development and provides an incentive to build long-lived structures in risky areas. This, in turn, causes property values to increase in some areas where protection is available and reinforces the political and economic arguments for even more protective measures. When relocation eventually becomes the only viable option, the economic losses are substantially higher for those affected, compared to those losses which would have been incurred from an early retreat.
There are difficult decisions to be made in balancing near-term sea level rise protection against more drastic steps to move people away from the coasts. But this research is suggesting that when communities focus excessively on reducing near-term threats, they risk inhibiting the successful adaptation that they are trying to promote.