The interconnected ecosystem, ridge to reef

The foresight to conserve the Main Ridge Forest “for the security of rainfall” must be extended to the coasts downstream and the coral reefs offshore in order to safeguard the quality of life on Tobago. This is the lesson from islanders on Hawai‘i.  Dr Anjani Ganase (@AnjGanase) addresses the issue of upstream misuse and downstream consequences in an extended version of the article written for the XL Catlin Seaview Survey blog in 2015 ( Follow @wildtobago on instagram, or for weekly articles in the Tobago Newsday.

In 2015, our coral reef survey team from the University of Queensland went to the reefs along Moloka‘i Island, Hawai‘i. Along this coast, we noticed several low rock wall structures made from lava rock adjacent to the coral reefs. Our skipper pointed out these structures, explaining that the Hawaiians built them about 800 years ago to rear fish to feed the villages.
In Molokai‘i, Hawai‘i, ancient loko kuapa (fishing ponds) line the coast adjacent to the coral reefs. Map data (USGS): Google, DigitalGlobe 2018

The early Hawaiians observed that marine fish were attracted to the sheltered brackish waters, using these habitats for grazing and as nurseries. They decided to reinforce these habitats near to the shore by building structures to create loko kuapa (ponds) that would attract and protect fish. The porous lava rocks allowed water to flow in and out of the ponds that varied in size among the Hawaiian Islands; some were as large as three or four square kilometres. 

The relationship with the coral reefs became obvious. The Hawaiians regarded the coral reefs as the source of diverse fish species, and worked with the natural ecosystem to ensure food security for their communities.

These clever early fish farmers designed ponds to maintain wave movements and connections to the open ocean. They also managed pond biology and the harvesting of the fish following the kapu (traditional rules). The fishponds were regulated for water circulation, nutrients, and observed for the size and abundances of fish species that entered the enclosures. The work of these ancient aquaculturists was key to sustaining the productivity of these ponds for hundreds of years, feeding thousands of Hawaiians daily. These techniques - rotating and harvesting fish in controlled habitats – were likely applied before they were developed in other countries.

After these fishponds were successfully used for hundreds of years, they went through a period of misuse when management practices waned. Today, restoration projects are underway to rebuild and revive the fishponds and rekindle the ancient connections to unified ecosystems. The communities are learning to rely on ancient aquaculture practices again. The younger generation is being reconnected to their traditional culture, and the sustainable management of resources. 

At a broader scope, traditionally, islands of Hawai‘i were divided into ahupua‘a – tracts that extend from the mountains to the reef or ocean, commonly along a watershed  - which were considered to be self-sustaining units. Communities that currently manage these fishponds are acutely aware of how upstream changes, such as agriculture runoff and deforestation can upset the balance of their ponds and coral reefs. This connection of the fishponds to the mountains above and the sea beyond was also known as ahupua‘a. The size of the ahupua‘a depended on the available resources, which were managed by the families living in different locations within the area. There was no such thing as private property, as the sustainability of the ahupua‘a relied on continuity and connectivity and thus land was never fenced off. Trade occurred upstream and downstream: farmers at the base of the mountains traded with fishermen on the coast; and wood for boats was sourced from the communities in the mountains. The caretakers in the mountains were responsible for not affecting the land and water conditions that fed into the rivers and coasts, while the aquaculturists and fishermen ensured that seafood harvest was maintained sustainably.
From ridge to reef - the mountains and the lush rainforests of Kaua‘i island, Hawai‘i stand prominently above the reef. Photo by Anjani Ganase

This is the premise of the management plan of the Hawai‘i Humpback Whale Sanctuary. Ecosystem-based management ensures healthy land-sea connections for productivity and benefits to the Hawaiian communities. Such management acknowledges that no animal, habitat or ecosystem occurs in isolation. Animals move around and migrate to other habitats. Mountain habitats supply the water to marshlands and ponds where juvenile fish can thrive and migrate to coral reefs and the ocean as adults.  

This type of management works within an island system. It is clear that rather than investing in isolated pockets of forests and coastline, we should protect and manage interconnected tracts of land and sea ecosystems for more efficient and effective outcomes. Ecosystem-based management – the Ridge to Reef concept – has been growing in Tobago, put forward by local institutions such as ERIC (Environmental Research Institute Charlotteville) and Environment Tobago; and The Cropper Foundation in Trinidad. Imagine the benefits to northeast Tobago if islanders would manage land and sea cohesively, as an integrated ecosystem.

Charlotteville in northeast Tobago, where ridge to reef, ecosystem-based management can be established. Photo by Anjani Ganase

At an even broader scale, the management of crucial habitats becomes more challenging, when we consider that the migratory and dispersal ranges of animal and plants cross national borders and into international water and airspace. Here in the Caribbean, our marine environments are shared by marine organisms that move or disperse between the islands. Marine turtles that nest on Tobago forage along coastlines of other Caribbean islands and enter other oceans. Dispersal of certain species of coral larvae to reseed coral reefs has the potential of dispersing at kilometre scale. Therefore, the protection of a reef connected by water currents to a reef that has been destroyed by a hurricane may be crucial for long-term recovery of the damaged reef and those fishermen and communities that depend on it. With growing understanding about connectivity of our ecosystems across borders; regional protection of essential habitats may be more effective at putting pressure on local enforcement. 

In time, I hope for equal respect for the ocean as for the land; the connectivity that the Hawaiians call Aloha ‘Aina (love of the land) and Aloha Kai (love of the ocean). Or as Sylvia Earle said even more succinctly, “No water, no life, no blue, no green!” 


Life in Early Hawaii, The Ahupua‘a, Third Edition, Kamehameha Schools Press Honolulu (1994)


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