Saving Oceanic Islands with the Vetiver System

Wednesday, June 12, 2013


Oceanic islands, no matter whether they are in the Pacific, (the world’s largest area of scattered tiny islands) or anywhere else in the world as long as they are between the latitudes of 30° North or South of the Equator, will depend on the Vetiver System for their future survival as viable habitats.

[This article is contributed by guest blogger John Greenfield - Director, The Vetiver Network International]

I developed the Vetiver System using contour rows of vetiver grass (Vetiveria zizanioides) over 50 years ago for the Fiji Sugar Industry to stabilize farm land in the Fiji Islands. It was extremely successful and is still there today. This system of sustainable hedges is fully applicable to all other tropical developing countries in order to sustain their agricultural production in every aspect.

Vetiver Systrem vs contour banks
Vetiver Systrem vs contour banks
The standard methods of constructed soil conservation still being taught at temperate climate universities throughout the world, do not work in the tropics and especially in tiny ocean islands exposed to short duration and high intensity rainstorms and hurricanes. The constructed system of ‘conservation’ is expensive to install. Because of its design characteristics, it takes up too much land to be properly installed, is short lived, and is extremely expensive to maintain. The constructed system is designed to collect runoff, divert it to a safe outlet and dispose of it ‘safely’. This is the last thing a rain-fed farmer on a small tropical island wants. The constructed system because it acts like a drain, is also the worst system for replenishing freshwater aquifers in these tiny island atolls. Rainfall must be evenly distributed over the surface so that it can find access to the aquifers and replenish them before being lost to the sea as runoff.

Recently, in the South Pacific, we have seen the devastation of the little island Niue as a result of a 300+ kilometer/hour hurricane. The island of Niue is typical of so many of these little islands and atolls, it is 260 square kilometers in size, has 4,108 ha of arable land of which 470 ha are, or were, in permanent crops. For sustained viability, this land and the surrounding marginal land will need stabilizing to prevent soil loss and runoff. This can only be done in the tropics using the Vetiver System, a dynamic system of hedges across the slopes around the island.  These hedges of vetiver (Chrysopogon zizanioides), once established, are permanent and effective barriers to soil loss and runoff. Ocean islands depend on rainfall to replenish their fresh water aquifers, usually on ‘perched-water tables’.

In their natural state, these little islands had some jungle cover which provided fuel wood and building material, but more importantly the jungle’s undergrowth and leaf-litter spread the rainfall run-off out, slowed it down, gave it a chance to seep into and replenish the natural aquifers before it ran in to the sea.

With greater population pressure in recent years - tourist resorts, paved roads, airport runways, and other constructions, these jungles - and especially the undergrowth - have been destroyed. Gardens which used to produce sufficient food to mix with the fish and shellfish from the reef and lagoons are now producing next to nothing. Runoff is uncontrolled; top soil is disappearing fast and, where it enters the sea polluted, it kills the reef. Not only are food stocks going down but, due to pollution, fish stocks in the lagoons are diminishing also. Where the coral of the barrier reef is damaged, there is no protection from the next hurricane, and the storm waves can now be devastating.

Tourism has created another major problem . . . rubbish. This trash, especially plastic containers, bottles, and
Vetiver on a beach - Bali
Vetiver on a beach - Bali
wrapping all non biodegradable. This is being dumped in the drainage network and eventually ends up out at sea. Vetiver hedges planted in the drainage network filters all this rubbish out of the runoff and holds it back for collection and proper disposal.

 In their present state, these islands can be supplied with food, health needs and infrastructure by aid agencies and the ‘outside world’. Because of their isolation, we cannot supply them with sufficient water (or soil), nor keep up the supply. Rainfall must be controlled so that it isn’t wasted as runoff or polluted by poor rubbish disposal; this is the only way to ensure water supplies to these little islands and keep them habitable. Very few of these small islands have any rivers or streams; they depend on rainfall to replenish their ‘perched water-tables’ - and the only way this can be done is by controlling the runoff and giving it a chance to soak in to the ground.

Vetiver grass hedgerows can be very valuable in preventing erosion and water damage to tracks, wells and gardens within the island’s housing areas, and in protecting roads (even against tsunamis which will go over the hedges and not under them). The hedgerows should be coupled with urban tree planting in housing areas, trees which could serve as shade as well as a source of timber; food; fuel or forage. When planted along embankments and in catchment areas, vetiver hedgerows can also reduce erosion of roadsides and airfields. If there are streams in the country, the hedgerows are also extremely important in permanently reducing stream bank erosion and sediment loads entering streams, reservoirs and harbors. The massive root system of the vetiver plant (measured down to six meters in Thailand) forms an extremely dense ‘underground bio-dam’ across the slope, and is capable of clarifying water and not only maintaining but increasing year around water flow of springs and streams by holding back runoff and giving it a chance to find an underground aquifer.

Because of their soil filtering function, natural terraces begin forming behind vetiver hedgerows soon after planting. Not only do hedgerows mitigate erosion, but empirical data indicate that the survival, growth and production of trees and annual crops planted behind the hedges can be increased by as much as 50% by conserving topsoil, increasing the availability of nutrients and moisture for these plants.

Vetiver grass hedges planted across the slope of steep hillsides establish extensive root systems and begin reducing erosion within the first year. A study by scientists from Texas A&M after Hurricane Mitch in Honduras, shows that erosion was reduced from "92 tons of soil/ha/yr to 0.9 tons/ha/yr on steep hillside farms that were protected by contour hedgerows of vetiver.” The only farms that weren’t destroyed during Hurricane Mitch, the most violent hurricane ever recorded, were those protected by vetiver hedges.

What is needed now is to get a small island as a demonstration area using the Vetiver System, to show the aid agencies the economic effectiveness of this system and be used as an example to the rest of the world’s ocean islands. We would need to get approval from the governing body of the island or island group to lay down such a demonstration covering the full benefits of the Vetiver System on one island. We would need to get approval to import the planting material, the experts and labor to lay out the demonstration and the funds to cover this plus a maintenance period of at least three seasons. We would also need to budget for a high-standard documentary to be made of the demonstration for further publicity of what can be done in such threatened areas . . . before it is too late.

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