Madagascar Tropical Dry Forest
Location:Madagascar is an island in the Indian Ocean off the southeastern coast of Africa. The entire island is about 228,900 square miles in size1 – making it the world’s fourth-largest island2 – and the tropical dry deciduous forest region on the island is about 58,400 square miles (including areas in both the north and west of the island)3. Here is a picture of where the island of Madagascar is located globally (1), and another picture of where on the island the tropical dry forest is located (2).
According to the World Wildlife Fund, about 97 percent of the western tropical dry forest region of the island has been destroyed, and the remaining portion of it is designated as critically endangered by that same organization.4
What was Madagascar’s tropical dry forest originally like? How is it different today?
Deforestation has caused significant changes in Madagascar’s tropical dry forest ecoregion. Scientists believe that originally (that is to say, 2000 years ago and before human habitation of the island) almost all of the 58,400 square mile ecoregion was covered with dry deciduous forest.5 This is an example of one patch of deciduous dry forest in Madagascar:
Currently, the ecoregion is composed of large swatches of secondary grassland interspersed with relatively small patches of dry deciduous forest. This deforestation, which is mostly due to intentional burning of the forests by humans, has had a severely negative impact on biodiversity. While the tropical dry forest of Madagascar is renowned for its biodiversity, particularly because it contains so many endemic species, the secondary grasslands which have grown in to replace the burned-out forests contain very little species diversity and are composed mostly of alien plants. Given the overwhelmingly negative effects on biodiversity that this deforestation has had, it’s fair to say that human impact on the dry forest bioregion of Madagascar has been at least bad if not ugly.
How and why have people changed the ecosystem?
Most of the tropical dry forest in Madagascar has unfortunately been degraded and destroyed by humans for timber and agriculture, as mentioned. Some intact forest remains, predominantly near the western coast, but moving further inland toward Madagascar’s central islands, only secondary growth areas can be found. A great deal of the diversity found in the tropical dry forest is lost as that land is converted to secondary grassland. Although various researches disagree as to the precise amount of intact tropical dry forest remaining on the island of Madagascar, the general consensus seems to be about 12,000 to 20,000 square kilometers7. Here are some diagrams showing the deforestation the entire island of Madagascar has experienced:
Source (for both images): Elmqvist, Thomas, Markku Pyykönen, Maria Tengö, Fanambinantsoa Rakotondrasoa, Elisabeth Rabakonandrianina, and Chantal Radimilahy. "Patterns of Loss and Regeneration of Tropical Dry Forest in Madagascar: The Social Institutional Context." Ed. Michael Somers. PLoS ONE 2.5 (2007): Fig. 5, 6. Web.
These data demonstrate an 11 percent decrease in
forest cover from 1984 to 2000 – but a 7 percent increase in forest cover from
1993 to 2000 is encouraging8.
Still, it’s important to keep in mind that most of the dry forest area
is composed of discontinuous fragments of forest, usually 35 square kilometers
in size at most.9 This diminishes the possibility for survival of
animals with ranges larger than that size.
Furthermore, although the majority of the larger blocks of tropical dry
forest that remain are found in protected areas, there are many other highly
endangered areas still in need of protection, and in fact the protection
supplied may be inadequate. This is in
large part because the methods used often don’t take into account the needs of
the people of Madagascar, many of whom had become accustomed to drawing on
these threatened ecosystems for essential goods and services (such as land for
agriculture).10
Types and Severity of Threats
The primary threat to the
dry, deciduous forests of Madagascar is posed by those seeking land to use for
agriculture or grazing. Often the forest
is intentionally burned down to make room for agriculture and grazing;
furthermore, secondary grasslands develop in areas that have been burned, and
these grasslands are extremely susceptible to wildfire. Wildfires that start in the secondary growth
areas adjacent to the dry forest will often spread into the remaining pockets
of dry forest11. The
purposeful burning of the forest is not likely to stop soon, though, as the
population of Madagascar’s inhabitants who rely on agriculture is increasing,
and the agricultural methods they use degrade the land even further. As a result, there is constant pressure to
clear more land for agricultural purposes.Logging is also a source of stress on the existing forest ecosystems, although selective logging is practiced and only the larger trees are normally removed.12 Even the forests which have been thoroughly selectively logged rather than burned to the ground cannot support many of the animal species endemic to the Madagascar dry forest, such as several types of lemur. In fact, some of the lemurs are hunted for food, which makes it even more difficult for the natural ecosystems to reestablish themselves, especially because lemurs play a critical role in seed dispersal of native plants13. Here is a picture of one such threatened lemur, Eulemur fulvus:
Not
only the forests themselves, but also the nearby wetlands and rivers are
threatened by deforestation. Burning
down the forests results in soil erosion, which in turn yields an inundation
with silt which the rivers and wetlands cannot handle.14
Overall, the situation in this
ecoregion of Madagascar is dire: it is
estimated that about 97 percent of the dry forest has been destroyed since
human habitation of Madagascar first began, and, as mentioned, the remaining 3
percent exists in isolated pockets.15 Thus the dry forest and
surrounding wetlands are significantly threatened by agricultural expansion,
and their many endemic plant and animal species are threatened as well.
Protected areas and their statuses:
As mentioned, several of
the remaining areas of tropical dry forest on Madagascar are protected
areas. Some studies, however, have found
that the administration of the protected tracts of land is not fully
effective. For example, one study found
that in Ankarafantsika National Park, because of the “limited means available
to the local authorities and the considerable size of the region,” there is
little prevent raffia (palm fiber) collectors who lack permits to form camps
and to hunt endangered animals (especially lemurs) to supplement their diets.16 Here is a woman from Madagascar weaving a basket from raffia palm:
Site: http://www.superstock.com/stock-photography/Madagascar+Palm
Furthermore, several critical sites, including the
Daraina region in the north and the Bemahara region in the south, remain
unprotected although many scientists agree they are in immediate need of
protection.17Site: http://www.superstock.com/stock-photography/Madagascar+Palm
Future of ecosystem:
If the environmental
destruction of Madagascar continues at the current rate, patches of native
vegetation will occur more and more greatly interspersed, as a result of the
burning of land for agricultural (as well as the burning of trees for
charcoal). Several key species are also
likely to become instinct or at least more critically endangered. For example, the endemic tree Hazomalania voyroni is on the verge of
extinction because it is cut down for timber and is highly prized by the Sakalava people of Madagascar for making
coffins.18 Other tree species
which are endangered due to deforestation include Givotia madagascariense, Cedrelopsis grevei, and Commifora arofy.19Also, several animal species are threatened by traditional hunting practices which continue even in protected areas. Furthermore, studies show that lemurs, which, as mentioned are important for seed dispersal, are particularly affected by decreasing forest fragment sizes. 20
How can we achieve a human/ecosystem balance?
Deforestation seems to be the most negative human impact on the dry deciduous forests of Madagascar, and current agricultural practices are clearly exacerbating the problem. However, it’s important to consider that for many subsistence farmers of the region, burning down forests is the most expedient way to clear land so that it can be used for agriculture. To give another example, people who make their living by gathering raffia from the dry forests of the Ankarafantsika area are also lacking in resources, and it’s difficult to blame them for hunting lemurs when they need food, even though the absence of these lemurs reduces seed dispersal and compounds the deforestation problem. Therefore, the best and most necessary way to combat deforestation would be to introduce alternative farming methods to Madagascar that don’t use monoculture and don’t require large expanses of cleared land. Another way to afford economic opportunity to residents of Madagascar who are currently subsistence farmers would be to increase ecotourism. If done well, focusing on ecotourism would in itself be an incentive for the government and the people of Madagascar to protect biodiversity on the island, since more people will want to visit if more of the natural environment remains intact. Furthermore, a greater emphasis on ecotourism would help to generate the political will necessary to fund adequate monitoring of national parks. If all these changes are implemented, Madagascar may remain a hotbed of biodiversity for decades to come.
Sources
1.
Bureau
of African Affairs. "Background Note: Madagascar". U.S. Department of
State.
2. Bureau
of African Affairs. "Background Note: Madagascar". U.S. Department of
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3.
Southern
Africa: Northwestern Madagascar at http://worldwildlife.org/ecoregions/at0202
5. Southern
Africa: Northwestern Madagascar at http://worldwildlife.org/ecoregions/at0202
6.
Bloesch,
Urs. "Fire as a Tool in the Management of a Savanna/dry Forest Reserve in
Madagascar." Applied Vegetation Science 2.1 (1999): 117-24. Web.
8.
Elmqvist,
Thomas, Markku Pyykönen, Maria Tengö, Fanambinantsoa Rakotondrasoa, Elisabeth
Rabakonandrianina, and Chantal Radimilahy. "Patterns of Loss and
Regeneration of Tropical Dry Forest in Madagascar: The Social Institutional
Context." Ed. Michael Somers. PLoS ONE 2.5 (2007). Web.
9. Southern Africa: Northwestern Madagascar at
http://worldwildlife.org/ecoregions/at0202
10. Ferraro, Paul J. "The Local Costs of
Establishing Protected Areas in Low-income Nations: Ranomafana National Park,
Madagascar." Ecological Economics 43.2-3 (2002): 261-75. Web.
11. Southern
Africa: Northwestern Madagascar at http://worldwildlife.org/ecoregions/at0202
12. Brown, K. A. "Long-term Impacts of
Logging on Forest Diversity in Madagascar." Proceedings of the National
Academy of Sciences 101.16 (2004): 6045-049. Web.
13. Ganzhorn, Jorg U., Joanna Fietz, Edmond
Rakotovao, Dorothea Schwab, and Dietmar Zinner. "Lemurs and the
Regeneration of Dry Deciduous Forest in Madagascar." Conservation Biology
13.4 (1999): 794-804. Web.
16. García, Gerardo, and Steven M. Goodman.
"Hunting of Protected Animals in the Parc National D'Ankarafantsika, North-western
Madagascar." Oryx 37.01 (2003): n. pag. Print.
17. Southern
Africa: Northwestern Madagascar at http:worldwildlife.org/ecoregions/0202
18. Rabearivony, Jeanneny, Eloi Fanameha, Jules
Mampiandra, and Russel Thorstrom. "Taboos and Social Contracts: Tools for
Ecosystemmanagement – Lessons from the Manambolomaty Lakes RAMSAR Site, Western
Madagascar." Madagascar Conservation & Development 3.1 (2008): 115-18.
Web.
20. Ganzhorn,
Jorg U., Joanna Fietz, Edmond Rakotovao, Dorothea Schwab, and Dietmar Zinner.
"Lemurs and the Regeneration of Dry Deciduous Forest in Madagascar."
Conservation Biology 13.4 (1999): 794-804. Web.
