Wednesday, 22 October 2014

The conservation status of Madagascan Palms.


Madagascar is considered to be one of the world’s biodiversity hotspots. The island has an area of 592 750 km2 and is located in the southern Indian Ocean, giving it a tropical climate with a diverse range of habitats. There is a range of mountains running from the north to the south of the island, which divide it into distinct climatic and environmental bands; the eastern part of the island having a much moister climate dominated by moist tropical forests, while the west of the island is more arid and dominated by dry thorn forests. Madagascar has been separated from all other landmasses since the Cretaceous, and has a unique flora and fauna comprised largely of species found nowhere else.

There are 195 known species of Palms found on Madagascar, of which 192 are known only from the island. 90% of these are restricted to the moist forests on the east side of the island, an environment considered to be particularly at risk; about 75% of these moist forests have been cleared to date and clearance is still ongoing in many areas. Palms are also targeted by humans for a variety of reasons, including for Palm hearts (which are consumed as food), timber for construction and, increasingly, collection for the horticulture industry.

In a paper published in the journal PLoS One on 30 July 2014, Mijoro Rakotoarinivo of the Kew Madagascar Conservation Centre in Antananarivo and John Dransfield, Steven Bachman, Justin Moat and William Baker of the Royal Botanic Gardens at Kew in the UK present a systematic review of the conservation status of the 192 indigenous Malagasy Palm species under the terms of the International Union for the Conservation of Nature’s Red List of Threatened Species; the first such assessment of Malagasy Palms published since 1995.

Rakotoarinivo et al. conclude that of the 192 known indigenous Malagasy Palm species, 61 species are Critically Endangered, 45 species are Endangered, 43 species are Vulnerable, 14 species are Near Threatened and 16 species are of Least Concern. 13 species were found to be Data Deficient; that is to say there was not sufficient information available to include them in the review.

Forest clearance for slash and burn cultivation by smallholder farmers, causing habitat loss for many species, such as Masoala kona (Endangered). William Baker in Rakotoarinivo et al. (2014).

The number of species considered to be at risk (Critically Endangered, Endangered and Vulnerable) has gone up since 1995, however this is in part due to the discovery of 28 new species of Palms since this time, 27 of which are considered to be at risk and 18 Critically Endangered (this is quite common; species with large populations and wide distributions are likely to have been discovered some time ago, so newly discovered species are often in high risk conservation categories); many of the newly described species are known only from very restricted areas, and several from less than 10 species.

Of the 130 species assessed in 1995, 80 have had no change in conservation status, while 32 species are considered to be less threatened than previously and 24 species are considered to be more threatened now than in 1995. While there have been some improvements in the protection of wild Palms in Madagascar, most notably the establishment of the new Système des Aires Protégéesde Madagascar Reserve network, many of the species considered to be at less risk than in 1995 are so considered because fieldwork by conservationists and botanists has discovered new populations of these plants, though 21 of the 32 less threatened species are still considered to be at risk.

Remnant populationsof species such as thisTahin aspectabilis (Critically Endangered), at Analalava, near Mahajanga, in vegetation remnants isolated within anthropogenic landscapes, are at risk fromfire, grazing and other human pressures. John Dransfield in Rakotoarinivo et al. (2014).

Rakotoarinivo et al. conclude that up to 83% of native Malagasy Palm species are currently threatened, making the group particularly threatened even for Madagascar (where 54% of plant species are considered to be threatened, compared to 21.5% of plant species globally). These Palms are at threat primarily due to human activity, particularly the clearing of forests for agriculture and unsustainable harvesting of wild Palms. Rakotoarinivo et al. note that the economic circumstances of Madagascar’s large rural communities are of particular importance to Palm conservation on the island, and that without economic changes that enable this population to change the way they live, forest clearances and unsustainable harvesting are likely to continue, making other conservation measures irrelevant.

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