File:Casuarina equisetifolia (ironwood) (San Salvador Island, Bahamas) 2 (15789786685).jpg

Casuarina equisetifolia Linnaeus, 1759 - ironwood (a.k.a. Australian pine) in the Bahamas.

Plants are multicellular, photosynthesizing eucaryotes. Most species occupy terrestrial environments, but they also occur in freshwater and saltwater aquatic environments. The oldest known land plants in the fossil record are Ordovician to Silurian. Land plant body fossils are known in Silurian sedimentary rocks - they are small and simple plants (e.g., Cooksonia). Fossil root traces in paleosol horizons are known in the Ordovician. During the Devonian, the first trees and forests appeared. Earth's initial forestation event occurred during the Middle to Late Paleozoic. Earth's continents have been partly to mostly covered with forests ever since the Late Devonian. Occasional mass extinction events temporarily removed much of Earth's plant ecosystems - this occurred at the Permian-Triassic boundary (251 million years ago) and the Cretaceous-Tertiary boundary (65 million years ago).

The most conspicuous group of living plants is the angiosperms, the flowering plants. They first unambiguously appeared in the fossil record during the Cretaceous. They quickly dominated Earth's terrestrial ecosystems, and have dominated ever since. This domination was due to the evolutionary success of flowers, which are structures that greatly aid angiosperm reproduction.

Superficially, the ironwoods shown above appear to be pine trees/conifers, but they're not - they are angiosperms (flowering plants). The specimens shown above are not native to the Bahamas. Ironwood occurs naturally in parts of southeastern Asia, Australia, and on many islands in the southwestern Pacific Basin. Ironwood was introduced to the Bahamas a couple centuries ago by the British as windbreaks between adjacent plantations. Casuarina has rapidly invaded much land in the Bahamas - its seeds are very mobile and indestructible in seawater.

It has been recently determined that Casuarina causes beach erosion, despite the perception that its roots prevent beach erosion. Casaurina shades out low-lying, native, back-beach vegetation. Its root systems are also toxic to native back-beach floras. After the sub-Casuarina vegetation dies and disappears, back-beach sand dunes get blown away, resulting in beach erosion. Casuarina is a much-favored shade tree in the Bahamas, so there’s been much resistance and skepticism by Bahamians about the detrimental aspects of the trees along shorelines.

Observations have indicated that, after storm damage, beaches rapidly re-establish themselves with normal native vegetation (without replanting, even) in the absence of Casuarina. No chronic beach erosion has been observed in the Bahamas except those beaches with Casuarina. Experimental removal of Casuarina from some shorelines has resulted in cessation of beach erosion and the natural replenishment of sandy beaches.

Classification: Plantae, Angiospermophyta, Fagales, Casuarinaceae

Locality: shoreline along southern side of Graham’s Harbour, northern margin of San Salvador Island, eastern Bahamas

Most info. provided by Neil Sealey.

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