December 9, 2007

A bunch of stuff you never wanted to know about Australian Pines

Shortly after I moved back to Florida in 1985, the county came and removed a line of Australian Pines (Casuarina Equisetifolia) near my grandmother's home in Boynton Beach. I was horrified that a beautiful stand of trees could be removed and nothing planted in their place.

While I was trying to find out who was responsible, the Palm Beach Post conveniently ran an article to explain; apparently, I wasn't the only person seeking answers.

As it turns out, that "beautiful stand of trees" was actually damaging the environment.

Since then, the State of Florida and the various municipalities have launched a formal campaign to remove the trees while it's still possible, and before the damage they cause becomes irreversible.

The program went smoothly until the state discovered a major infestation of Citrus Canker. Citrus trees are NOT harmful, and thousands of Floridians enjoyed backyard access to oranges, grapefruit, limes and more. Until someone decided that if destroying every citrus tree within 500 feet of an infected tree slowed the spread of infection, then destroying every tree within 1800 feet would slow it more. The State started the wholesale slaughter of backyard citrus, trampling civil rights and common sense in the process.

And ultimately, they failed to stop the citrus canker.

On the heels of this dismally wretched program, folks started to question the removal of the Australian Pines. After all, if the state screwed up so bad with the canker eradication, maybe they don't really know that Australian Pines are bad.

I've seen a few blogs and columns and web pages that decry the removal and destruction of the invasive Australian Pine. Michael Mayo's blog entry in the Sun-Sentinel started nagging at my conscience, but it's when I read an entry in one of my favorite blogs that I finally realized it's time to set the record straight about Australian Pines.

Some poorly informed individuals even claim that the reasons for their removal is based on "pseudo-science." There are dozens of studies to support the cause of removal. There are NONE that conclude that Australian Pines are safe. So which is the "pseudo-science:" the side that can produce studies back as far as 1960, or the side that hasn't produced a single peer-review study?

I will use the list provided by Ken Ellis on his "Save the Australian Pines" website, as it is typical of the arguments against the removal of Australian Pines. It's also convenient to refer to it, as it's already set up with bullet points.
Aesthetic value: It provides shade which is in short supply in Florida. Few if any native plants can provide the shade of a mature Australian pine. The "needles" that the Australian pines drop make a perfect matting around picnic tables. Their rustic appearance adds character to the parks. And the wind blowing through their branches gives a soothing sound.

Historical heritage: The Australian pine is a part of South Florida's historical heritage. It is a reminder of the people who first developed the Gold Coast area of Florida. I feel that some of this heritage needs to be preserved, even protected. And what better place to preserve heritage than in public parks?

Where should Australian pines be removed first: Should we start by removing them from public Parks where they are being enjoyed or should we start by removing them from areas that are not used by people and where their removal will be less of an impact. I suggest that efforts be concentrated on first removing Australian pines in areas not used by the public and LAST removing them from the Parks. Actually, after all the Australian pines that are not in Parks have been removed, we should probably declare them an endangered species and preserve and protect the ones in the Parks

Taking over South Florida: The Australian pines... seem to have been "planted" rather than just spreading. As far as I know, they are propagated by roots, not birds carrying their seeds

"MAY" be allopathic: ..several statements ... say Australian pines "MAY" be allopathic, that is, their needles or roots may give off a chemical that discourages other plants from growing nearby. If this is true, why hasn't anyone proven it?

Out compete native species: Since the Australian pine is such a hearty species, highly tolerant of salt spray and the poor soils of beaches, it would seem to me that it would be particularly desirable to have them along the coast line where the salty conditions make it difficult for many plants to grow, especially close to the beach

Roots shallow and wash out easily: It seems to me that the roots of the Australian pine go much deeper and wider than any of the native plants and would therefore tend to hold the dunes in place better than the native plants. Even if an Australian pine is blown over, its roots would still help to protect the dunes from erosion

Wind break: Removal of the Australian pines from the beach areas will remove a wind break that is currently protecting the homes to the west

Disposing of the Australian pines: The people who are currently cutting down the Australian pines in South Beach Park in Boca Raton, Florida are not making any effort to save or use the wood. They are using chain saws to cut the trees into about 2' chunks and then grinding them up to make mountains of mulch. They also seem to be leaving the stumps behind.

1: Aesthetic Value.

I agree that stands of Australian Pines are lovely; I think ALL trees are lovely. And I agree we need more shade trees in Florida; too many palms are planted. Ironically, palms are planted purely for aesthetic reasons; they have no value for shade or wind breaks or erosion control.

The problem is that Australian Pines provide TOO MUCH shade. According to the University of Florida:
"Australian pine's dense shade and leaf litter retard the growth of native coastal vegetation (Schardt and Schmitz 1990)"
There are species that NEED shade to flourish. But they need SOME light. Native trees provide
the right mix of shade and dappled light, or they grow far enough apart for light to diffuse into the shady regions. Australian Pines don't do any of that. In fact, every study notes that stands of Australian Pines tend to consist entirely of Australian Pines. The exact phrase is "monoculture."
So what's wrong with that? Since the Pines have no natural containment, they will eventually replace all other flora in the environment. They will become the sole wind break and erosion control in the ecosystem. But because there is only one species performing this task, it leaves the environment susceptible to disaster. If the Australian Pines ever suffer a blight, they will ALL die, and there will be NO windbreak, shade or erosion control AT ALL.

Historical heritage: (The Australian pine is a part of South Florida's historical heritage.)

So was dumping our raw sewage into the rivers and estuaries. That was destructive; we don't do it anymore because we discovered it was HARMFUL. Surely, no one will argue that we should dump raw sewage into our lakes because it's "our heritage."

3. Where should Australian pines be removed first:

Mr. Ellis proposes removing trees from public parks LAST. But the thing is, the State and various public entities actually OWN those areas, so there's no question of access or civil rights violation. Remember the Citrus Canker fuss about going onto private property?

The State is correct to remove the pines from parks and public spaces; not only because there's no paperwork to do so, but because they can study the process of removing and replacing the trees. This will make the process of removing privately sited trees much easier.

4. Taking over South Florida:

Mr. Ellis argues that Australian Pines
'...have been "planted" rather than just spreading. As far as I know, they are propagated by roots, not birds carrying their seeds.'
Australian Pines' seeds are carried by wind. They have winged seeds for this purpose, and they produce them all year long.

It's curious that Mr. Ellis notes that birds aren't carrying the seeds: birds carry seeds by eating them and pooping 'em out later. He's just admitted that birds don't feed on Australian Pines.

5. "MAY" be allopathic:

ARE allelopathic. There is absolutely no doubt about this at all, it's very widely documented.

The Florida Exotic Pest Council reports:
"Produces allelopathic compounds that inhibit growth of other vegetation (morton, 1980]"
Perdue University reports:
"Asparagine and glutamine accounted for 92% of the total amino acid in the nodules. The bark contains 10% catchol tannin, the root 15%."
Example of the effects of allelopathic soil under Australian Pines

I think the confusion comes from the fact that allelopathic compounds are not solely responsible for preventing undergrowth; most reports cite that lack of native undergrowth "MAY BE due to allelopathic compounds." As noted earlier, the deep shade is also responsible, as are the dense beds of fallen needles. But Australian Pines absolutely change the soil chemistry.

6. Out compete native species:

I've already mentioned the dangers of monoculture. But I will also point out that Mr. Ellis as tacitly admitted that no native wildlife feed on them. The local fauna feeds on the local flora; if there is no local flora, the local fauna dies. At some point, the Australian Pines WILL edge out some critical local plant, and it will have a cascade effect.

According to the Plant Conservation Alliance,
"Once established, it radically alters the light, temperature, and soil chemistry regimes of beach habitats, as it out-competes and displaces native plant species and destroys habitat for native insects and other wildlife."

7. Roots shallow and wash out easily:
8. Wind break: (provides a critical wind break)

Mr. Ellis believes "that the roots of the Australian pine go much deeper and wider than any of the native plants." He doesn't say WHY he believes this. He offers no factual basis for his belief whatsoever.

But plenty of experts disagree with him:

Plant Conservation Alliance;
"Unlike native shrubbery, the thick, shallow roots of Australian pine make it much more susceptible to blow-over during high wind events, leading to increased beach and dune erosion and interference with the nesting activities of sea turtles.
The Florida Exotic Pest Control Council:
"Encourages beach erosion by displacing deep rooted native vegetation"
The Smithsonian Institute:
"The thick, shallow and wide-spreading roots are both disruptive to lawns and pavement and also make the tree prone to being overblown in strong winds (e.g., hurricanes). Casuarina equisetifolia grows too tall to be considered a safe ornamental tree given its tendancy to blow over."
"...the tree's thick, shallow roots actually make it more likely to be blown over in high winds than most coastal native trees. Wind-felled C. equisetifolia can exacerbate erosion on beaches and dunes..."
The Nature Conservancy:
"Very young Casuarina (Australian Pine) seedlings are capable of trapping sand because of their close scrubby growth, but once Casuarina grows beyond the sapling stage, it ceases to trap sand because of the lack of low, shrubby vegetation around the trunk. Casuarina monocultures are usually flat without dune-swale topography and lack diversity in understory vegetation. The shallow root systems of the trees makes them susceptible to toppling during storms (Digiamberardino 1986)."

The University of Miami:
"In areas where the Australian pine establishes, native, dune building species are out competed and the coastline becomes altered from a dune, stable coast to a flat, unstable shore with a recessed coastline, susceptible to erosion (Sealey 2003)."

Evolution of naturally vegetated beaches versus Casuarina sp. (Australian pine) dominated.Neil Sealey, 2003

9. Disposing of the Australian pines
Mr. Ellis complains "The people who are currently cutting down the Australian pines ... are not making any effort to save or use the wood." But he then goes on to say they are "grinding them up to make mountains of mulch." Hey, mulch is a use.

Beyond that, the number one use is as firewood. Not a lot of call for that in Florida. And before you can burn it, it takes 3-5 years to "cure." That's a fancy term meaning "dry out."

10. Replacing what has been destroyed
Mr. Ellis concludes that we'd save all kinds of money simply by not removing the trees. This is akin to saying that you can save money by not treating your cancer, or by not buying insulin to treat diabetes. Sure, you save the initial outlay, but in the end you pay more than you would have in the first place.

Sure, stands of Australian Pines are pretty. But the true cost of those "pretty trees" is higher than we should pay:
  • Destruction of property and endangerment of life and limb when the trees get blown over.
  • Increase in erosion along our beaches.
  • Loss of native habitat.
  • Destruction of native ecosystem
  • Extinction of endangered species.
Oh, hey, I forgot to tell you about the turtles and crocodiles!

I've described the thick roots of the Australian Pine. Here's photo of them along a beach.

Note that the roots create a fairly steep bank above the tide line. These exposed roots prevent turtles and crocodiles from accessing their nesting grounds. Not only do they have a hard time crossing the roots of the stand trees, where the trees have fallen over, the roots prevent turtles and crocodiles from getting to the zone of beach were they dig their nests.

But even if they get over and through the roots and find a place where they can dig their nests, there's too much shade; the eggs never hatch.

The fact of the matter is that Australian Pines really ARE destructive to our environment. I do agree that they should be replaced with native shade trees. It is unfortunate - but necessary - that those trees will take time to grow into the peaceful refuge on a sunny day. But better a few years of inconvenience than the ultimate destruction of habitat that is the only promise of Australian Pines.

Here's a bibliography of additional resources:
Binggeli P. 1997. Casuarina equisetifolia L. (Casuarinaceae), Woody Plant Ecology. Available online.

Duke J.A., 1983 Casuarina equisetifolia J.R. and G. Forst., Center for New Crops and Plant Products, Purdue University.

Elfers S.C. 1988. Element Stewardship Abstract for Casuarina equisetifolia. The Nature Conservancy. Unpublished report prepared for The Nature Conservancy on Australian pine. Winter Park, FL.

FLEPPC. 2005. List of Florida's Invasive Species. Florida Exotic Pest Plant Council. Available online.

Langeland K.A., and K.C. Burks (Eds.). 1998. Identification and Biology of Non-Native Plants in Florida's Natural Areas. UF/IFAS. 165 p.

Moler P.E. 1991. American crocodile nest survey and monitoring. Final Report to Study No. 7533, Florida Game and Fresh Water Fish Commission, Bureau of Wildlife Research, Tallahassee FL.

Morton J.F. 1980. The Australian pine or beefwood (Casuarina equisetifolia L.), an invasive "weed" tree in Florida. In: Proceedings,Florida State Horticultural Society 93:87-95.

Snyder S. A. 1992 SPECIES: Casuarina spp., U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Fire Effects Information System.

Swearingen J.M. 1997. Australian Pine. Washington, D.C. National Park Service, Plant Conservation Alliance, Alien Plant Working Group. Available online.

Whistler W.A., and C.R. Elevitch. 2006 Casuarina equisetifolia (beach she-oak), C.cunninghamiana (river she-oak); Casuarinaceae (casuarina family). Species profiles for Pacific Island agroforestry ecological, economic, and cultural renewal. Available online.


  1. Excellent article. Lots of research. A couple of points –

    The state and city does NOT own the parks. The citizens, the people, own it. The administrators work for us. They might want to ask their bosses (us) before they destroy the beauty of a park.

    Replace the trees with trees!!!!
    If you cut down a 100 foot beautiful tree, replace it with a tree at least 20 foot tall. A REAL tree! Not those stupid twigs that won't grow any taller than 10 feet and will blow over the first time a fat bus driver walks by and farts.

    And don’t replace them with palm trees, which if I recall, most of them aren’t really native either.

    Rip up concrete parking lots, mow down abandoned buildings and old strip malls, stop building more roads, and stop the chemical companies from polluting the environment first, then attack the trees.

    Interesting how there are people from Dow AgroSciences and Aquatic Vegetation Control, Inc. serving on the Florida Exotic Pest Plant Council. I wonder what their real interests might be?

    The bottom line is there are two facts. I’ll agree, finally, that Australian Pines have more negatives than positives. I’ll even go so far to say they may be bad for the environment. But the other fact is people love them! Really love them. So, let’s tackle the other far more serious problems first, before we rip out the trees.


  2. The state and city does NOT own the parks. The citizens, the people, own it.

    That's a circular argument: the government, state, local, and federal, is The People. Our leaders come from us, and we elect them.

    Replace the trees with trees!

    I agree, but you can't simply plant new trees in the hole left by the Australian Pine: the soil has been contaminated, and it takes some time for the toxins to break down.

    don’t replace them with palm trees,

    No argument from me on that. Palms are NOT trees, and they do dick for shade.

    let’s tackle the other far more serious problems first, before we rip out the trees.

    While ripping out the parking lots and strip malls should happen, they only break down with time. Australian Pines, on the other hand, spawn MORE Australian Pines, destroy MORE native flora and fauna, and cause MORE erosion. They have to be dealt with immediately, because if they aren't the problem will only get much, much bigger.

    They are a cancer, and they are killing our state. Sure, they're pretty. They are pretty cancerous growths. They're tumors.

  3. Good post. These trees do look nice and all, but they are bad. Period.

  4. I have a few Huge Australian pines on my property ,, spreading like wild fire .. I must constantly destroy new growths that form from their shallow roots . they really do take over at an alarming rate .