A High Concentration Of Coastal Development And Population Density Results In Cumulative Impacts to the Ecosystem

The majority of visitor accommodations, local human population, and infrastructure are along the coastline in Hawaiʻi. This high concentration of coastal development and population density results in most human activities taking place in and adjacent to the nearshore environment. 

Agricultural and golf course runoff can introduce nutrients from fertilizers and chemicals such as pesticides and herbicides to coastal ecosystems. 

Urban runoff can deliver a broad spectrum of land-based pollution that degrades nearshore water quality, with cascading effects on coral ecosystem health. Poor water quality can also undermine the natural defense abilities of corals and increase the likelihood of mortality from heat stress.

Aquarium fishing is reported to the State of Hawaiʻi Division of Aquatic Resources (DAR) separately from food fish, under a different licensing scheme and reporting system. Catch of aquarium species for the years 2003 - 2015 was mapped as the average annual number of individuals taken by reporting block (which differ slightly from commercial reporting blocks above). Seaward extent of reporting blocks was limited to 60 m depth and units were calculated to the number of individuals taken per hectare.

Nearshore fisheries in the Main Hawaiian Islands encompass a variety of fisheries in which multiple gear types are used to harvest reef finfishes and invertebrates, estuarine species, and schooling coastal pelagic fishes. Communities in Hawaiʻi often rely on these fisheries for economic, social, and cultural services. Stress from over-fishing can cause ecosystem degradation and long-term economic loss.

Sediment from coastal erosion and various land-based activities can affect reef health by covering corals, blocking light, and inhibiting new coral settlement. This can lead to degradation of reef ecosystems. To quantify sedimentation, we modeled how much sediment was being transported into the nearshore marine environment around the Main Hawaiian Islands.

There are over 95,000 onsite sewage disposal systems (OSDS) (i.e., cesspools and septic tanks) used in Hawaiʻi, many close to coastlines and streams. These systems have varying levels of treatment capacity for nutrients, bacteria, and other pollutants found in wastewater and may leech into groundwater that flows to the ocean. Excess nutrients can promote rapid algal growth, outcompeting corals and disrupting the natural balance of the ecosystem.