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MELALEUCA The Everglades’ second-biggest threat OMNI Earth column, 1995 By Eddie Huffman Call it the tree that ate the Everglades. Melaleuca trees suck wetlands dry and bully out native plants, putting serious stress on an already overstressed ecosystem. It's not

melaleuca forests too dense to accomodate anything but the trees themselves. From an ill-advised airplane seed drop in the early part of the century to an ongoing,

as if the Everglades lacks enemies, since development, fire, and an unhealthy water supply already besiege it on all fronts. But the melaleuca ranks as one of the

tree-by-tree fight

The trees were introduced by a young scientist named

against the invader decades later, the melaleuca has made

John Gifford intent on

quite a name for itself

transforming the "mucky

trees were introduced

wasteland" of the

Everglades' most


serious threats,

in South Florida. The by a young scientist named John Gifford intent on transforming the

second only to humans altering the

"mucky wasteland" of the Everglades into a

ecosystem for development and farming.

more hospitable climate for the state's

The tree grows at a rate of 52 acres per day,

human inhabitants. Colleagues mailed

transforming diverse marshlands supporting

Gifford a packet of melaleuca seeds from its

native plants and animals into dried-up

native Australia, where natural enemies

keep the tree in check. No one seems to

many trees per acre. The tupelo gum, for

know the exact year Gifford tossed his

instance, which is a standard tree in the

seeds, though experts think it was in the

paper and pulp industry, will have about

early '20s. "From an airplane, he threw the

250 trees per acre. In a melaleuca forest,

trees out in two different epicenters in the

there are trees every 18 inches to 2 feet." In

eastern Everglades," says Mike Scott, a

other words, 2,000-4,000 trees per acre.

biologist who has studied melaleucas

That density helps explain why the

extensively and who heads the Jupiter-

melaleuca poses such a threat to the

based Florida Mitigation Trust. "It started

Everglades. A mature melaleuca forest dries

thriving, and it spreads when the trees are

up the groundwater; leaf growth and

agitated." Estimates of the land impacted by

transpiration require a lot of water, and

the melaleuca range from 300,000 to 1.5

melaleucas have a lot of leaves to suck up

million acres. University of Miami biology

water and release it into the atmosphere.

professor Ron Hofstetter, who has studied

Because of the tree's substantial leaf area,

melaleucas since 1970, ranks the tree as the

Hofstetter says, 10 square feet of melaleuca

Everglades' No. 2 threat.

pump four times as much water into the atmosphere as a comparable stand of saw

In a melaleuca forest, there are trees every 18 inches to 2 feet.

grass. With the melaleuca's dense canopy blocking sunlight to the ground below and a chemical in its leaves preventing the growth of other plants around the tree, the melaleuca excludes all other vegetation, in turn eliminating food sources and habitats

Melaleuca encroachments can range from a lone tree on an acre of land to

for wildlife. Traumatize a melaleuca by cutting or

thousands of times that number in a mature

burning it and the tree fights back hard,

forest. Scott has discovered the tree's shock

releasing seeds by the millions. Its papery

value: "I'll take people in the paper industry

bark is thick and heavy with water, making

out to a melaleuca stand and they'll say,

it hard to destroy by fire. When a melaleuca

`This is incredible.' They've never seen so

does burn it burns explosively, unleashing

chemicals that can cause painful allergic

similar work in the name of "wetlands

reactions in people downwind. "There

mitigation," using money that developers

probably isn't a plant that is better suited to

must pay into a fund when converting

the Everglades than the melaleuca,"

wetlands. To counterbalance the

Hofstetter says. The tree thrives in a

melaleuca's natural defense mechanisms,

subtropical climate, grows in organic or

Forestry Resources and other combatants

mineral soils, and can survive both frost and

haul the trees away before their seed pods

fire. A single melaleuca may hold millions

open, then go back to the cleared forest to

of tiny seeds in its seed pods, and any stress

curtail the growth of any new seedlings by

on a melaleuca -- from burning a tree to

burning or spraying herbicide on them. That

chopping one down -- causes those seed

kind of mechanical control is one of three

pods to open. While the tree won't take root

methods currently being employed or

in a wetland deeper than three feet or so,

studied to combat the tree. "It's not the total

once established it can survive constant

answer," says John Cauthen, president of

flooding. Unlike Australia, in Florida the

Forestry Resources. "Certainly it's a pretty

only thing keeping the melaleuca in check

healthy part of the total solution."

is man. The tree has a few negligible virtues: Melaleuca oil is used in some skin creams and tooth polishes, and the tree is used ornamentally in parts of Florida and Southern California. Forestry Resources of

Unlike Australia, in Florida the only thing keeping the melaleuca in check is man.

Ft. Myers, has found a positive use for the melaleuca that also helps control its spread. The company clears melaleuca forests, chips the trees into mulch (sold under such brand names as Enviromulch and Florimulch), and reintroduces native vegetation to the cleared ground. Scott's company, the Florida Mitigation Trust, does

The rest of the solution involves chemical control and biocontrol. Chemical control means spraying herbicides on the trees, done en masse from the air or ground in dry areas and on a tree-by-tree basis in areas of open water. Again, any effort to kill

melaleucas requires followup work in

from Australia, arriving nearly a century

which new seedlings are destroyed by

after John Gifford's initial packet of seeds.

flood, fire, or chemicals, or by simply

"If we can stop the spread of it, then that's a

pulling them up out of the ground.

major accomplishment," says Robert F.

Biocontrol is still in the research stages,

Doren, assistant research director for

with scientists studying the use of insects

Everglades National Park. "We will never

that will attack melaleuca seed pods and

get rid of the melaleuca completely. It's just

new seedlings. It is both ironic and fitting

not possible."

that the weevils and sawflies under consideration for biocontrol are imports

Melaleuca: the Everglades' second-biggest threat