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I am writing in response to the Community Voice article by Gordon LaBedz on June 25 (“Decisions To ‘Harden’ Hawaii Beaches Can Be Disastrous”). He states that the “majority of Hawaiian beaches are eroding,” but does not say why. Sea level rise in the past 40 years is only 3.5 inches.

In this time, beaches have lost many feet of sand vertically, so SLR is not the cause. One can’t just say “climate change,” since there is no evidence of increased storm activity.

So, what is the cause? Scientific investigations by the Keonenui Bay Foundation have found the answer.

Coral reefs dissipate up to 97% of wave energy. Conversely, taking away a coral reef increases wave energy hitting shore 30 times. Coral reef extent in Maui has significantly decreased during the past few decades. Why is this?

Water runoff in Maui is very polluted, with agricultural and landscaping runoff, animal waste, wastewater injection and raw sewage from tens of thousands of cesspools. Areas with more pollution have smaller coral reefs and less sand.

For example, Mokuleia Bay in West Maui had a slaughterhouse above it and has lost 90% of its beach between 1912 and 1997. There were never seawalls.

Another example is Maalaea Bay, where large pollution has been documented. Its coral reefs, described in 1972 as “striking in their diversity and in the presence of rare corals species,” was reduced to 8% live coverage by 2007. Its beaches are mostly gone and several condominium buildings are threatened.

Mr. LaBedz’s statement that “If nature wanted a reef, one would have grown there” ignores the well-documented reduction of coral reefs in Hawaii.

Therefore, destroying coral reefs allows more wave energy to reach shore, eroding sand. Building seawalls is a last-ditch effort to save structures and does accelerate erosion of remaining sand, but erosion continues even without a seawall.

However, when seawalls are removed, soil is washed into the ocean causing brown water and killing marine life, so it may be best to keep seawalls. Managed retreat does not stop this erosion.

The only solution is to restore the wave energy dissipation function of coral reefs. Measurements show that for wave energy dissipation, the most important reef characteristics are a top within 2 feet of the ocean surface, a width large enough so that steepening waves break on the reef, and a rough surface to cause turbulence.

Coral reefs act as breakwaters, but are below the surface and are permeable, so water easily flows in and out and stagnant water as in Hilo Bay does not occur. Building artificial reefs offshore does not impact shore activities or disturb cultural areas.

There are many methods of installing concrete forms or rocks to form a reef. Concrete used is not hostile to coral settlement and growth, but coral grows slowly in high wave energy locations. installation of concrete reefs is very expensive, sizes are limited, and storms move and knock them down. Natural growth of coral to the required size takes centuries, so coral nursery transplantation is not a solution.

The best solution is Biorock Mineral Accretion. Steel mesh is welded into a form and attached to the seabed. Biorock has survived 30-foot hurricane waves unscathed. A harmless electric current changes the local chemistry, resulting in hard calcium carbonate forming on the steel.

Coral grows faster by a factor of 4.4, bleaching survival is increased a factor of 3.5, settlement rate is increased a factor of 26 and corals are immune to ocean acidification. Within about five years, a coral reef copy is grown.

Beach sand has been restored every time Biorock was properly constructed and maintained. A constellation of Biorock modules totaling a half-acre in area can be installed in West Maui bays for about $250,000.

The only organization to incorporate mineral accretion into a rugged, economical and long-lasting system is the Global Coral Reef Alliance. It is run by Tom Goreau, who has a Harvard Ph.D. in biogeochemistry and has spent 30 years perfecting Biorock. He has worked with several indigenous Pacific island communities.

Not restoring energy dissipating reefs will eventually cause an ecological and economic catastrophe for Maui.