Hawaii's intertidal zones are one of the most accessible ocean zones, which has lead to various negative impacts on its health. The coastlines in Hawaii are considered of high value, especially to hotels companies (i.e hotels in Waikiki). Therefore, certain anthropogenic activities play a big part in the degradation of intertidal zone health, an important one being coastal development. Intertidal zones are also expected to be most impacted in the future by climate change, invasions (invasive species), eutrophication (excessive amounts of nutrients, leading to algal blooms), and overharvesting (Cox et al 2013).
Coastal Development
Development poses a threat to intertidal zones because it fragments and/or displaces the zone and the species that live there. The seawalls at Ukumehame, Maui are a good example of how intertidal zone health are negatively impacted. Ukumehame was originally a beach, but the beach washed away throughout the years after the seawall was built. Seawalls are intended to stop coastal erosion; however, it ends up altering the natural movement of sand with tides and waves. This results in much of the sand washing away into the ocean and increasing erosion.
Erosion directly impacts other zones as well because as the land continues to erode, sediment begins to cover the coral reefs, blocking it from receiving sunlight. Since the coral reefs are not receiving the necessary sunlight to grow, these conditions will favor algal blooms to occur, in which algae overgrow and suffocate the coral reefs. Algal blooms not only suffocate the coral reefs, but also decrease the amount of habitat available to reef species.
Erosion directly impacts other zones as well because as the land continues to erode, sediment begins to cover the coral reefs, blocking it from receiving sunlight. Since the coral reefs are not receiving the necessary sunlight to grow, these conditions will favor algal blooms to occur, in which algae overgrow and suffocate the coral reefs. Algal blooms not only suffocate the coral reefs, but also decrease the amount of habitat available to reef species.
Sea Level Rise
Sea level rise due to climate change (human caused) is also another major threat to the intertidal zone. Over time, species have adapted to live in certain parts of the intertidal zone where they benefit that ecosystem the most. However, since sea level is increasing at a faster rate, species need to be able to adapt quicker. Most species will not be able to adapt This may result in the extinction of many native species and the increase in invasive species, which is extremely detrimental to intertidal zone ecosystems. Sea level rise can be intensified by storm surges during hurricanes, which are unusual and large increases in water levels (NOAA). An example of this is the photo below, showing a road damaged by breaking waves during Hurricane Sandy.
Invasive Species
Hawaiʻi's ecosystems are extremely threatened by the presence of invasive species and it's expected to only get worse in the future. When thinking of invasive species in Hawaiʻi's intertidal zones, mangroves tend to come to mind. Even though this species is important to other pacific island ecosystems, mangroves in Hawaiʻi have caused substantial damage to our coastlines by overgrowing native habitat. One of the main concerns with mangroves in intertidal zones is that they will limit the ability to restore native wetland ecosystems (Allen, 1998). Paepae o Heʻeia in Kaneʻohe, Oʻahu have been working tirelessly since 2001 to remove the mangroves growing there (paepaeoheeia.org).
Overharvesting
Overharvesting of species in intertidal zones are not as common as other ocean zones, but they still do have an effect, especially on ʻopihi. The more exposed/accessible areas with ʻopihi have been the most negatively impacted. Out of the three ʻopihi species, Kōʻele populations are the least threatened, which is most likely due to their difficult accessibility by people. ʻĀlinalina and makaiauli are the species that people mainly harvest for consumption. The most favorite tasting of the three ʻopihi species are ʻālinalina. In 1970, laws were set in place to regulate ʻopihi picking (DLNR, 1981), however did not seem to hold since populations are still on a rapid decline. However, there are laws being proposed to better maintain ʻopihi populations around the islands. At local scales, organizations such as The Nature Conservancy, Haleakalā National Park, and Kīpahulu ʻOhana have collaborated together to create ʻopihi rest areas in Haleakalā National Park, Kīpahulu District. These ʻopihi rest areas are no-take zones for three years to promote the recovery of ʻopihi populations.