Green Pages

Cedar Trees: Friend or Foe?

What impact does the Australian pine have on the local plant community?
Story & Photos By Chloe Hardman
Tall trees waving in the winds are a common sight along the beautiful beaches of the Turks & Caicos. Locally known as the cedar, these trees offer pleasant shade. But have you ever stopped to wonder where these trees came from?
History
Very few people alive today will remember a time when there were no cedar trees on the Islands. Historical records tell us the cedar trees were introduced to Florida in the late 1800s from Australia. They probably reached the Turks & Caicos around a similar time. This origin gives rise to another name for the tree: the Australian pine.
Although they look like pines, these trees are not true pines. The scientific name for these cedar trees is Casuarina equisetifolia. Having leaves reduced to tiny scales around thin branchlets gives the appearance of needles. What look like cones are the fruiting heads which are dispersed by birds, wind and water. One pound of these fruiting heads can contain up to 300,000 seeds. This is just one feature that makes the cedar tree spread so rapidly.
Spreading fast
Have you noticed an increase in the number of cedar trees on the Islands? Many people have. Bambarra and Whitby Beaches on Middle and North Caicos, respectively, are areas along which you may have noticed the trees spreading over the years. You may have also seen them along roads or wherever land has been cleared.
Why do these trees grow so well along beaches and roads? Colonising bare sandy soil is not easy for many plants. It is a dry, salty environment with few nutrients. Casuarina trees have a partnership with microbes, helping them to fix nitrogen from the air into the soil. Being salt tolerant and fast growing also helps.
Impact on other species
Being such fast growers gives Casuarina trees a competitive advantage over some other plants. There is concern that they displace native vegetation. In Florida the tree is considered a serious pest and is thought to interfere with turtle and alligator nesting. When a species spreads rapidly and causes harm it is classed as invasive. I am interested to find out what impact the Casuarina is having on the native plant community in TCI.
To investigate this I have been recording the plants growing under the Casuarina and comparing this to the plants growing outside of it. Many people told me “nothing grows under the Casuarina,” so I was surprised when I found a range of species growing under it. However the abundance of plants does appear to be lower under Casuarina, especially in areas that have been recently cleared.
Combination of threats
Casuarina is a plant that likes to grow where humans have disturbed the environment. It is often the first plant to grow back in a cleared area and puts down a carpet of needles and shade making it harder for other plants to grow. There is no doubt the dune communities would look very different without it. The further into the bush humans take bulldozers, the more Casuarina will grow and change the landscape.
Values and choices
The Turks & Caicos Islands are home to some truly unique natural habitats. Nine species of plants are found no where else on earth except these Islands. In contrast Casuarina trees are found on hundreds of islands across the world and form monocultures in areas which once were diverse.
What type of landscape do you value? On one hand, the Islands could end up looking like many other places in the world. On the other hand, leaving important areas of unique natural habitats whilst sensitively developing other areas could help preserve natural heritage. The choices the people of Turks & Caicos Islands make in developing the landscapes will determine which route is taken.
My research into the invasive plants on Turks & Caicos is part of my MSc degree in Conservation Science at Imperial College London, UK. I would like to thank the Turks & Caicos National Trust for working with me, particularly B. Naqqi Manco, Ethlyn Gibbs-Williams, Melanie Visaya, Bob McMeekin and Miranda Jones. The trip would not have been possible without the fantastic support of the Royal Botanic Gardens, Kew, UK, especially Martin Hamilton and Marcella Corcoran. Also, to the many people who have talked to me about the local plants, thank you for your time and insight.

What impact does the Australian pine have on the local plant community?

Story & Photos By Chloe Hardman

This dense mat of Casuarina needles can prevent other plants from growing.

This dense mat of Casuarina needles can prevent other plants from growing.

Tall trees waving in the winds are a common sight along the beautiful beaches of the Turks & Caicos. Locally known as the cedar, these trees offer pleasant shade. But have you ever stopped to wonder where these trees came from?

History

Very few people alive today will remember a time when there were no cedar trees on the Islands. Historical records tell us the cedar trees were introduced to Florida in the late 1800s from Australia. They probably reached the Turks & Caicos around a similar time. This origin gives rise to another name for the tree: the Australian pine.

Although they look like pines, these trees are not true pines. The scientific name for these cedar trees is Casuarina equisetifolia. Having leaves reduced to tiny scales around thin branchlets gives the appearance of needles. What look like cones are the fruiting heads which are dispersed by birds, wind and water. One pound of these fruiting heads can contain up to 300,000 seeds. This is just one feature that makes the cedar tree spread so rapidly.

Spreading fast

Have you noticed an increase in the number of cedar trees on the Islands? Many people have. Bambarra and Whitby Beaches on Middle and North Caicos, respectively, are areas along which you may have noticed the trees spreading over the years. You may have also seen them along roads or wherever land has been cleared.

Why do these trees grow so well along beaches and roads? Colonising bare sandy soil is not easy for many plants. It is a dry, salty environment with few nutrients. Casuarina trees have a partnership with microbes, helping them to fix nitrogen from the air into the soil. Being salt tolerant and fast growing also helps.

Impact on other species

Being such fast growers gives Casuarina trees a competitive advantage over some other plants. There is concern that they displace native vegetation. In Florida the tree is considered a serious pest and is thought to interfere with turtle and alligator nesting. When a species spreads rapidly and causes harm it is classed as invasive. I am interested to find out what impact the Casuarina is having on the native plant community in TCI.

To investigate this I have been recording the plants growing under the Casuarina and comparing this to the plants growing outside of it. Many people told me “nothing grows under the Casuarina,” so I was surprised when I found a range of species growing under it. However the abundance of plants does appear to be lower under Casuarina, especially in areas that have been recently cleared.

Combination of threats

Casuarina is a plant that likes to grow where humans have disturbed the environment. It is often the first plant to grow back in a cleared area and puts down a carpet of needles and shade making it harder for other plants to grow. There is no doubt the dune communities would look very different without it. The further into the bush humans take bulldozers, the more Casuarina will grow and change the landscape.

Values and choices

The Turks & Caicos Islands are home to some truly unique natural habitats. Nine species of plants are found no where else on earth except these Islands. In contrast Casuarina trees are found on hundreds of islands across the world and form monocultures in areas which once were diverse.

What type of landscape do you value? On one hand, the Islands could end up looking like many other places in the world. On the other hand, leaving important areas of unique natural habitats whilst sensitively developing other areas could help preserve natural heritage. The choices the people of Turks & Caicos Islands make in developing the landscapes will determine which route is taken.

My research into the invasive plants on Turks & Caicos is part of my MSc degree in Conservation Science at Imperial College London, UK. I would like to thank the Turks & Caicos National Trust for working with me, particularly B. Naqqi Manco, Ethlyn Gibbs-Williams, Melanie Visaya, Bob McMeekin and Miranda Jones. The trip would not have been possible without the fantastic support of the Royal Botanic Gardens, Kew, UK, especially Martin Hamilton and Marcella Corcoran. Also, to the many people who have talked to me about the local plants, thank you for your time and insight.



1 Comment

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Jimmy L. Shirley
Jul 1, 2010 17:28

The Australian Pine is a beautiful tree. Gives a fantastic shade and a beautiful sound when the wind blows. It does not keep grass from growing under it. You should see my front yard, I have a large one that is about 40 or 50 years old and very large and beautiful. The grass is just as thick under this tree as it is anywhere in my yard. Compared to the Palm Tree there is no comparison. The Palm Tree gives no shade and the long stems and leaves are constantly dropping in your yard. (I have 14 of them along with my Australian Pine) There are so many false stories about this tree that it is not funny. My wife and I went on a nature boat ride and we stopped at a small island in the inland waterway and got out with the naturalist who was conducting the trip. There were a number of Australian pines on the island along with mangroves. She was talking about the Mangroves and we started walking back and we passed a fairly large Australian Pine and she said “See that tree, it’s an Australian Pine, they are a terrible tree and they have been outlawed in the state of Florida. “The problem with these Pines is that they send down a tap root and when the tap root reaches salt water it withers up and dies. After it does that the first strong wind that comes along just blows the tree right over. I felt like grabbing her and throwing her off the island.
The county we are in “Manatee” just loves to plant palm trees, they constantly need to be trimmed to keep the branches from falling on the ground and if you are going out on a picnic and you sit in the shade of a 30 foot palm tree (only about 25 feet of shade on ground) before you know it the sun has moved enough that you will have to move your picnic table to a new location.
The Australian Pine has no maintenance.

Thanks for listening to me, It’s a shame that the people in Tallahassee (Our Capitol) have been brainwashed by some so called expert.
Your Friend: Jim Shirley

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