There are many reasons to save the wetlands for the future. There is the need to preserve biological species. There are many plants and animals that can only survive in these habitats, and many endemic species that exist nowhere else. For these we need to preserve the wetlands. We need to provide a continuity of habitat to allow these species to continue to live, thrive, and survive.
We also need to provide a large enough area, for all these species to have a viable population size to be able to cope with temporary fluctuations in living conditions such as dry periods, wet periods, occasional tsunamis, hurricanes, brushfires, pollution, poaching, predation, disease, and other negative environmental factors. Breeding populations should ideally be as large as possible for any species to ensure a genetic diversity that increases that population’s resilience. Preserving these wetland and riparian areas provides foraging grounds, and allows a large enough supply of food, and prey species.
Wetlands are under threat: Wetlands are constantly under threat from both natural and manmade factors. The number one cause of wetland loss in Kula Kai is development. Humans have a huge capacity to modify their environment and destroy natural areas like wetlands. It is estimated that we have already lost over 80 percent of our wetlands in Hawaii and maybe much more. More wetlands are being lost to development each year. Most wetlands in Hawaii are on private land, even though they are an important public asset. These wetlands provide many services to the community and to the natural environment, yet they have relatively few protections.
Wetlands affected by Sea Level Rise (SLR): Just like our coastlines and beaches, wetlands too will be impacted by the current trend of SLR. In as little as 10-15 years we could be losing 1/3 of our beaches, and up to half could be lost by 2050. However, if we make room for wetlands to migrate, we can keep them alive for future generations to enjoy. When SLR happens, some coastal wetlands can move or “migrate” inland, this is a process called “Marsh Migration“. In the right circumstances wetlands will be able to adapt themselves to changing conditions and reconfigure themselves to new conditions. We need to understand these processes and give wetlands the room they need to adapt and change.
Tsunami Threat: Tsunamis can be very devastating to coastal areas. And coastal wetlands too are extremely vulnerable to tsunamis. The mechanical action of the waves can strip away the vegetation and scour away the soil and permanently alter the topography of an area. It is conceivable to lose almost 100% of all species in a wetland from a single large tsunami. Even a small tsunami of a few feet or so can also damage wetlands as they can dump massive amounts of salt water into the system that can overstress or even kill species with salt-shock.
Coastal Erosion: Coastal erosion is prevalent in Hawaii, and this is due do several factors including SLR, but also degraded coral reefs, sand extraction, pollution, engineered coastal armoring, and overdevelopment of the coastline. Coastal erosion affects beaches and estuaries, and in turn the coastal wetlands. And unfortunately, once wetlands are negatively impacted, they will lose some of their ability to protect the coastlines, and the process of coastal erosion can accelerate.
Siltation: Wetlands, especially in the floodplain of Kīhei are vulnerable and susceptible to siltation. Siltation happens when stormwater bring silt down from the mountain, it builds up in the low-lying areas of the wetlands, gullies, and gulches. Layers of silt build up over time and reduce the wetland’s ability to hold water and support its biology. We have seen many once-thriving wetlands in Kīhei become gradually buried over time. This can happen slowly over decades, and many older local residents (Kūpuna) can remember far different conditions within the span of their own lifetimes. But alarmingly, there can also be measurable changes in soil levels even after a single storm event.
Non-point source pollution: We call this type of problem “non-point source pollution”, and this process is well known. The problem is not due to the wetlands but starts much higher up the watershed, in the catchment areas. Loose soils and deforested areas create faster rates of erosion, and this soil and silt is transported downslope with every rain. What we see at the coast down on the floodplain is the ground level gradually rising, and the amount of surface water diminishing.
Wetland and streambed restoration: Wetlands can be renewed and restored, and streambeds can be recovered using various methodologies. The siltation process itself is a natural one, but the problem we see in Maui Nui is the extreme nature of this process. This process has been accelerated by anthropomorphic changes to the landscape, namely farming, farm animals, deforestation, and urban development, plus some natural factors such as uncontrolled feral ungulates (axis deer, pigs, goats) that loosen the soil and eat the covering vegetation.
Wetlands for climate-change resilience: We know that wetlands provide many services that help to make our environment more resilient to climate change. Climate change will increase storm severity and we are expecting more extreme rainfall intensity and volume. This means more flash-flooding and more water flowing over the landscape. Climate change also leads to SLR that harms the coastline. We know that wetlands help protect coastlines by protecting coral reefs. But what we do not generally hear about is that SLR will also bring about rising water tables.
Rising Water tables: Rising water tables will become an issue for anyone who ever built something on the floodplain in a low-lying area, or wetland. Low-lying areas will become wetter, and localized flooding will become more frequent, and it will take longer for all this stormwater to drain away.
Importance of natural and green drainage infrastructure: This is why we must also consider open spaces, riparian areas, and wetlands past and present, as our essential drainage infrastructure. All of these natural watershed features (as well engineered “green” infrastructure that mimics natural systems) will have an ever-increasing important role in flood mitigation. These are the places that will be taking on the floodwaters, and they are the de facto stormwater detention areas and functional drainage infrastructures.
Cultural and Historical Preservation: Another reason to preserve wetlands is to preserve any potential cultural, historical, and archeological materials that might be found there. We know that Hawaiian settlements were centered around wetlands and streams and integrated these wetlands into their communal activities. So, this is usually where we find the highest concentrations of artifacts and archeological sites. When we preserve a wetland and riparian area we may be preserving valuable, information, for future generations to study. We do not yet have the technology to fully investigate all of the potential archeological sites in Kula Kai, but future generations may have. We owe it to our keiki to preserve the cultural and historical sites so that they can also have to opportunity to make discoveries, do research, and learn from the past. However, once a wetland is excavated, filled over, or built on, we lose the possibility of future archeological research.
Compatible uses: Not all types of wetlands need to be restored to original pristine condition to be preserved. There are other, non-destructive uses that can preserve subsurface archeology for future generations, or that could allow for the wetland to be rehabilitated at a later time. Many wetlands in Kula Kai have been used as agricultural lands in the past, and these uses could continue until such time that that might need to be turned back to fully functioning wetlands.
Mitigated and man-made Wetlands: There is also a huge potential for wetlands to be created where none existed before. But certain conditions namely the specific hydrological conditions, must exist for this to be viable. Our wetlands exist where they do because of conducive geologic conditions beneath the surface that create pathways for groundwater to move beneath the ground and come close to the surface. This is why wetlands can stay wet for long periods between rain events. There may be certain areas with suitable conditions that could be turned into a manmade wetland, but this is obviously far less desirable and far more expensive than preserving the ones that we already have.
Restoring former wetlands: As far as wetland creation and mitigation are concerned, it would be far simpler to look at the places that were former wetlands, that have the underlying hydrology that could be turned back into functional wetlands. These could be areas that are currently being used for parks, parking areas, and agricultural lands, that were former wetlands in days past.
We need to keep our options open, because change is certain, and climate change will force us to reevaluate our priorities, and to reassess the importance of natural watershed infrastructure, especially the benefits of wetlands.