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Conservation and Restoration of Sandy Cay

Conservation and Restoration
of the Bahamian Island,
Sandy Cay
By Edgar M. Fortune

The Exuma islands are located in the Bahamas -- 35 miles south-east of Nassau or about 90 minutes by air from Miami. The Exu-mas are a collection of over 365 cays and islands stretching over 120 miles with the two main islands of Great Exuma and Little Exuma. The total population consists of approxi-mately 7,500 people. The people rely on farming, fishing and tourism for their livelihood. These once obscure, small islands are now a very popular tourism destination in the Car-ibbean. With world-class resorts in the construction phase, and island temperatures aver-aging in the mid-70’s all year around, Exuma will surely attract the rich and famous along with the problems inherent of discovery.

There is a sign that warns people to respect the endangered iguanas that live here. In the early 90’s, a popu-lation density study was performed and biologist estimated that only 150-200 iguanas exist. Due to inva-sive species, the iguana population was in peril of extermination. The introduction of rats, rattus ssp. and one lone raccoon (that was ulti-mately removed by a conservation biologist) also contributed to these low numbers.

Protected Population
In mid 2004, I had the opportunity to visit two populations of rare iguanas in the Bahamas. The first part of the trip was to Sandy Cay, a small cay, or low–lying sandy coral island that is about 25 hectares (or about 61 acres) in size. Sandy Cay is home to the only known population of the Sandy Cay Iguana, Cyclura r. cristata. In the early 1990’s...a biologist estimated that only 150-200 iguanas exist.

Three other reptile species inhabit Sandy Cay, two species of Anole and one Sphaero-dactylus ssp. In addition, several species of birds nest on the island, Laughing gull, Os-prey, Antillian nighthawk, Zenaida dove, White-crowned pigeon, Grey kingbird, Baha-mian mockingbird, Royal tern and Wison’s plover. Several avian species migrate through the area, including the Green heron, Black-necked stilt and peregrine falcons.
Invasion of Australian Pine

Australian pine, Casuarina equisitifolia, has aggres-sively colonized parts of Sandy Cay – an otherwise pristine island. Australian pine is a deciduous tree; other common names include beefwood, ironwood, she-oak and horsetail tree. Australian pine can grow to 46 m (150 ft) and 10-20 cm (4-8 in) in diameter and is native to Australia, south Pacific Islands and Southeast Asia. Australian pine was introduced to the United States in the late 1800’s and disseminated throughout Florida and the Caribbean by the turn of the century. The most common Casuarinas es-tablished in central and southern Florida include three species: Casuarina equisitfolia, C. cunninghamiana and C. glauca. Common uses for these trees include ornamental purposes, windbreaks, hardwood, pulpwood, tannin and shade. Unfortunately, casua-rinas have proven inadequate for every application.

The Florida exotic pest and plant counsel list Australian pine as a category “1” plant. Category “1” plant species are defined as an “invasive exotic” that is altering native plant species communities by displacing native species, changing community structures or ecological functions. When established, it alters temperature, light and chemistry of soils which drastically affects the native plants and animals beneath it. Australian pine has shallow roots that rarely penetrate very deep into the soil, which can encourage beach erosion by displacing deep-rooted native vegetation. In addition, they interfere with the nesting of endangered sea turtles and the American crocodile (Klukas, 1969). The Australian pine reproduces prolifically by seed, and is dispersed by avian species, wind, water and fruiting heads float .With rapid growth of 5-10 ft. a year, dense shade, dense litter accumulation, allelopathic compounds that inhibit growth of other vegeta-tion; it is difficult for other plant species to compete.

Our team with the Global Insular Conservation Society (GICS) has conducted two habitat restoration pro-jects on Sandy Cay May 19-28, 2011 and May 23-June 6, 2009. The primary task of our restoration effort has been to eradicate the Casuarina tree. This tree has the potential to degrade the Sandy Cay iguana’s habitat by shading out the animal’s food plants.

A characteristic of the Casuarina is its ability to re-sprout from its extensive root system once the main trunk is cut. Some previous cutting of the Casuarinas on Sandy Cay has left acres of foot-tall trees sprouting from the intact root systems. Consequently, our removal technique has been the application of a systemic herbicide to the stump of the tree immedi-ately after cutting. This “cut stump” method assures that the entire root system of the tree will be killed, and it minimizes the risk of impacting other plants and animal.

Our team has achieved an approximate 80% kill rate of Casuarina using brush application of a Trichlopyr herbicide in a diluted formula widely marketed as “Brush and Stump Kil-ler.” A two-person crew can make quick work of an undisturbed grove of Casuarinas. One person cuts the tree down with a chain saw while the second, properly garbed in personal protective gear, immediately brushes the herbicide onto the stump. If the stump is not coated promptly it will “heal” inhibiting absorption of the chemical. Eradication becomes much more tedious when dealing with myriad small trees sprouting from Casuarina roots. In this instance, a team member usually works kneeling, moving across the ground while cutting the thin stems with loppers and then painting. We anticipate at least one more trip to Sandy Cay to substantially eliminate the Casuarina. The larger trees, potential seed sources have been a priority for removal.

As with any invasive removal effort, years of follow-up moni-toring will be needed. Nonethe-less, our small-scale project does approach the goal of re-storing Sandy Cay to its original condition and protecting this unique species of iguana.

In 2011, the iguana population appears very strong. I have observed many hatchlings, including a variety of different body sizes of iguanas. In addition, we were able to cap-ture 15-20 animals so we could process them. Processing includes taking measurements (including head vent (HV) and tail), assessing health, implanting transponders and deter-mining sex.

The Bahamas as seen from space. Photo courtesy of Wikipedia.

Sandy Cay Iguana 

Setting up camp

Australian Pine, Causuarina equistitfolia. Photo courtesy of Wikipedia.

The only sure way to truly get rid of invasive Austra-lian Pine in the Sandy Cay

Taking snout to vent measurement

Bahamas, Sandy Cay Iguana basking