Paleoecology, Ecological Restoration, and the Resilience of Hawaiian Ecosystems

In March of 2011 the largest tsunami in nearly 50 years hit Maui.  Although this was not a particularly destructive wave by historical standards, it gave the HILT staff an excellent opportunity to examine the resilience of the coastal ecosystem at Waihe`e that we had spent nearly a decade restoring.  At first glance the power and velocity of the wave appeared to have done substantial damage in one particularly low spot.  However, on closer inspection it became it obvious that the indigenous Naupaka, Pohinahina, `Anapanapa and `Akia that we had planted had, incredibly, endured the velocity and power of the waves and had held the soil in place.  The effectiveness of these native species in preventing and reducing the damage stood in stark contrast to the scouring and massive erosion seen just a short distance down the coast, where invasive species dominated.  While we had always suspected that ecologically restored ecosystems would be resilient to these types of disturbances, the March, 2011 tsunami confirmed the value of this work.

While our ecological restoration work was validated, ensuring a truly resilient ecosystem rests on several important assumptions, namely that we can reestablish the appropriate species in a given area.  Doing this requires reconstructing what a healthy ecosystem once looked like.  The past holds the key to the future, and by learning about the past, we can create a more resilient future both on HILT lands as well as across Hawai`i and the world.  As climate change brings about substantive changes to our islands, we need to discern ways of adapting to more intense storms, sea level rise and loss of coastal ecosystems.  With all of the human-induced changes to our coastal ecosystems in the past 50 years, many areas of Hawai`i are particularly vulnerable.  Now is the time to learn how to restore, adapt and change in order to make our islands more resilient. 

With this in mind, HILT staff have begun explorations of the paleoecology of our refuges.  Simply put, paleoecology is the study of past ecosystems, particularly the function and composition of vegetation across landscapes.  Sediment coring is among the most basic and common ways of reconstructing the vegetation at a location at various periods of time.  Generally, three micro-fossils are examined, two from plants, phytoliths and pollen, and the fossil remains of a single-celled organism known as a diatom.

Coring Team after a day in the mud at Nuu, Maui

Coring Team after a day in the mud at Nuu, Maui

In early 2016 HILT staff and volunteers gathered at the Nu`u Pond, and with the assistance of Cultural Surveys Hawai`i, extracted and examined a number of micro-fossils embedded in the wetland sediment.   Collectively, these micro-fossils help to paint a picture of the environment and vegetation at the Nu’u pond extending back approximately 2,000 years; long before the first humans arrived on Maui.   The data we were able to extract at Nu’u revealed several species present at the pond over a millennium ago, but that no longer exist anywhere near the refuge today. Through our coring work we were able to determine that the typically upland tree species Kolea (Myrsine) was the most dominant tree in the area in the centuries before humans arrived, while the grass Kawelu (Erograstis variablis) and the shrub Aweoweo (Chenopodium sp.) were found abundantly in the region.  Perhaps most important, however, the region maintained incredible biodiversity, and the diverse flora helped to maintain a resilient ecosystem, capable of withstanding substantial ecological disturbances, such as floods and tsunami. Today, these species no longer occur in the vicinity of the Nu`u Pond, with a near monoculture of Kiawe (Prosopis pallida) dominant today.

 While the information we learned from the sediment coring will help guide us in our ecological restoration work, our ultimate goal lies in making the refuges more resilient to storms, tsunami and the inevitability of climate change.  There is no discernible ‘magic bullet’ to making an ecosystem resilient to such things as major storms or climate change.   However, following the model of nature itself, the biodiversity of a healthy, productive ecosystem is inherently more resilient than one dominated by a monoculture of exotic and invasive species.  As we are face the threats of climate change, many known but some unknown, resilience has become an important focus of our ecological restoration work.  The key to resilience lies in biodiversity, and gaining a window into the past through paleoecology research guides the direction we take in restoring ecosystem biodiversity.  

 Plans are in the works to core the Waihe’e wetlands next.  While it is exciting to speculate about what we might find, whatever is revealed will help us recreate the past, and prepare for the future.  This raw data taken from the cores in Waihe’e will be taken to the United Kingdom to be analyzed at the University of Leicester’s  Palaeoecology Lab, part of the Department of Environment Sciences.  Information learned in this process will be shared here in the second half of 2018, so please check back then.

By, Scott Fisher, PhD.