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1. Past Climate Change and Biological Response
The diversity of climates encountered on Madagascar as well as the astonishing climate
variability in the past have contributed significantly to the patterns of endemism seen
today in Madagascar’s plants and animals. Climate changes which occurred during past
glaciations have been used to understand the mechanisms controlling the distribution
patterns of some modern taxa (Wilmé et al. 2006, Wilmé and Callamander 2006). This
analysis identified refuges, processes of dispersion and centers of endemism, and
suggested that riverine corridors allowed species migration in response to climate change,
while areas between the major river watersheds were isolated from one another, enabling
diversification that resulted in high levels of endemism. Higher refuges have sometimes
been proposed on higher mountains in Madagascar or on the central highlands with relict
populations of vertebrates or plants (ex. Rakotondrainibe 2000, Andreone et al. 2005).
But, contrary to the African continent, the role of refuges played by high mountains in
Africa (ex. Brühl 1997) does not clearly show up from the several hundred distribution
maps we have produced for Madagascar vertebrate taxa. On the other hand when taking
into account the orographic effects which are well documented on eastern and western
slopes of the island, it seems that the rivers with high headwaters could maintain a
ripiculous forest during the driest periods of last glaciations. Paleo-refuges of the dry
periods are thus the ripiculous forests which were maintained by the rivers which take
their sources at high altitudes. When the climate became wetter again, the riparian
habitats extended along the tributaries with headwaters at increasingly lower altitudes,
thus opening corridors of dispersion from the highest waterways to tributaries with lower
headwaters. The watersheds of these rivers with high headwaters are thus considered as
retreat watersheds when the climate is dry, and as dispersion watershed when the climate
becomes wet.
Major climate changes in Madagascar accompanied both deep time climatic variation and
global glaciations. Periods of both drier and cooler and wetter and hotter conditions
have been recorded, as well as rapid transitions between different climates (Wells 2003).
None of Madagascar’s mountains reach 3000m elevation, and only three have summits
above 2500m: Tsaratanana (Maromokotro 2876m), Ankaratra (Tsiafajavona 2642m), and
Andringitra (Boby 2658m) from north to south. However, rivers with high headwaters
could have maintained riparian forest during the driest periods of recent glaciations.
Paleo-refuges during the dry periods may have been linked to riverine habitat maintained
by the rivers that take their sources at high altitudes (Figure 2, watersheds A-J). When the
climate became wetter again, the riparian habitats extended along the tributaries with
headwaters at increasingly lower altitudes, thus opening corridors of dispersion from the
highest waterways to tributaries with lower headwaters (Wilmé et al. 2006). Rivers with
their sources at high elevation are thus considered as retreat watersheds when the climate
is dry, and as dispersion watersheds when the climate becomes wet. Watersheds situated
between retreat-dispersion watersheds and drained by rivers taking their source at lower
elevations (Figure 2, watersheds 1-12) were isolated during dry periods, lacked a highaltitude source of runoff, and underwent retraction or loss of their riparian habitats as the
climate and rivers dried out. Those rivers with lower headwaters were thus more isolated
and vulnerable to climate change, and consequently evolved high levels of endemism
Distribution pattern of many taxa can be explained under this hypothesis of high
watersheds providing riparian connectivity and low watersheds developing endemism
due to isolation, including diurnal and nocturnal lemurs. Preliminary analyses carried out
on a sampling of 2000 plant taxa of Madagascar indicate that Malagasy plants conform to
this same scenario and these centers of endemism (Lowry et. al. in prep). Therefore both
the riverine corridors and the intervening isolated forest blocks of higher endemism are
critical features to maintain as climate changes due to human action in the future.
See Fig S1. for further details on preliminary analysis. From a sample of 1198 plant taxa
(15,133 mapped records), 639 taxa show a distribution which conforms to the retreatdispersal hypothesis
Caption for Fig S1
Figure S1: Distribution of 1198 plant taxa endemic to Madagascar from a sample used by
APAPC project (Raharimampionona et al. 2005) including 15,133 georeferenced
records. Numbers are numbers of taxa localized to the 12 centers of micro-endemism
defined by Wilmé et al. 2006 and Wilmé & Callmander 2006.
References
Andreone, F, Cadle, JE, Cox, N, Glaw, F, Nussbaum, RA, Raxworthy, CJ, Stuart, SN,
Vallan, D, Vences, M. 2005. Species review of amphibian extinction risks in
Madagascar: conclusions from the global amphibian assessment. Conservation
Biology 19: 1790-1802.
Brühl, CA. 1997. Flightless insects: a test case for historical relationships of Africa
mountains. Journal of Biogeography 24: 233-250.
Dewar, RE, Richard, AF. 2007. Evolution in the hypervariable environment of
Madagascar. Proceedings of the National Academy of Sciences of the United States
of America 104(34): 13723-13727.
Ganzhorn, JU, Sorg, JP. 1996. Ecology and Economy of a Tropical Dry Forest in
Madagascar. Primate Report, Special Issue, Deutsches Primatenzentrum, Göttingen
46: 1-382.
Perrier de la Bâthie, H. 1921. La végétation malgache. Annales du Musée Colonial de
Marseille, série 3, 9: 1-273.
Rakotondrainibe, F. 2000. La flore ptéridologique d'une forêt relictuelle sur les hauts
Plateaux de Madagascar (la Réserve Spéciale d'Ambohitantely). In J. Ratsirarson &
S.M., Goodman (Eds.) Monographie de la forêt d'Ambohitantely. Recherches pour
le Développement, Série Sciences Biologiques. Centre d'Information et de
Documentation Scientifique et Technique, Antananarivo 16: 37-51.
Raharimampionona, J., Andriambololonera, S., Schatz, G.E., Lowry II, P.P.,
Rabarimanarivo M., Ratodisoa, A., & Ravololomanana, N. 2005. Identification des
aires prioritaires pour la conservation des plantes à Madagascar: utilisation des
données botaniques pour définir les priorités en matière de conservation. In: S.A.
Ghazanfar & H. Beentje (Eds.), African Plants: Biodiversity, Ecology,
Phytogeography and Taxonomy. Royal Botanic Gardens, Kew.
Wilmé, L. & M.W. Callmander. 2006a. Les populations reliques de primates: les
Propithèques. Lemur News 11: 24-31
Wilme L, Goodman SM, Ganzhorn JU. 2006. Biogeographic evolution of Madagascar's
microendemic biota. Science 312: 1063-1065.
2. Species Distribution Modeling for Projecting Biological Response
Species distribution models for 74 plant species were created using Maxent (Phillips et al.
2006, Phillips and Dudik 2008). The modeling methods follow those described in detail
in Kremen et al. (2008) with three improvements to the methods i) logistic outputs were
used ii) species specific thresholds were applied during the removal of biogeographic
over-prediction from the current (~2000) distribution, and iii) sample bias was removed
by selecting a random sample of background data drawn from the sampling distribution,
and the resulting models were fitted to current and future climate conditions. Nine
climate variables were used (Appendix 1). Current climate models were downloaded
from the WorldClim website (www.worldclim.org), and future climate layers for 2080
were prepared under three different Coupled Atmospheric-Oceanic General Circulation
Models: (1) CCCM (Canadian Center for Climate Change Modeling); (2) CSIRO
(Commonwealth Scientific and Industrial Research Organization, Australia); and (3)
HadCM3 (Hadley Centre, United Kingdom), and for two different IPCC
(Intergovernmental Panel on Climate Change) response scenarios (A and B). Percent
forest cover, derived from forest change maps (Harper et al.2007) was included as a
continuous variable, and was assumed to remain constant between current and future
climate conditions. Geology was the only categorical variable used. For the future the
predictions were constrained beyond the range of each variable that is currently
experienced across the whole of Madagascar, so no prediction was made where the future
climate does not have a current analogue.
Models and scenarios for future climate in Madagascar predict significant changes by
2080 in the distributions of nearly all of the 74 species examined. We found a high
degree of agreement between the six future predictions, made using the three climate
models (CCM, CSIRO, and HadCM3) and the two IPCC scenarios (A2a and B2a); with
19% of species predicted to expand, and 45% predicted to contract, under all of the six
future models. 36% of species had mixed predictions, with between one and five of the
six future models indicating contraction.
References
Harper, G., Steininger, M., Tucker, C., Juhn, D. & Hawkins, F. 2007 Fifty years of
deforestation and forest fragmentation in Madagascar. Environ. Cons. 34, 325–333
Kremen, C., Cameron, A., Moilanen, A., Phillips, S., Thomas, C. D., Beentje, H.,
Dransfield, J., Fisher, B. L., Glaw, F., Good, T. C., Harper, G. J., Hijmans, R. J.,
Lees, D. C., Louis, E. Jr., Nussbaum, R. A., Raxworthy, C. J., Razafimpahanana, A.,
Schatz, G. E., Vences, M., Vieites, D. R., Wright, P. C. & Zjhra, M. L. 2008 Aligning
conservation priorities across taxa in Madagascar with high-resolution planning tools.
Science 320, 222–226
Phillips, S. J., Anderson, R. P. & Schapire, R. E. 2006 Maximum entropy modeling of
species geographic distributions. Ecol. Modelling 190, 231–259.
Phillips, S. J. & Dudik, M. 2008 Modeling of species distributions with Maxent: new
extensions and a comprehensive evaluation. Ecography 31, 161–175.
3. Calculating Restoration and Plantation Costs
Restoration Costs
The cost estimate of USD $850/ha for restoring natural habitat were derived as an
average based on restoration of multiple habitat types through several projects going on
across Madagascar. Approximately 4.5 million hectares of natural forest will remain
outside of formal protection once expansion of the protected areas’ network is completed.
Plantation Costs
The cost estimate for plantations of USD $360/ha is based on eucalyptus plantations in
eastern Madagascar.
4. Maximum REDD Income
Maximum REDD income is calculated as
Max REDD income=Country's total deforestation carbon (tons/yr) x $10/ton
Deforestation carbon=Deforestation rate (yr^-1) x Forest area (Ha) x Carbon density
(tons/Ha)
International policy based on historic national baseline is assumed. National
deforestation rates and standing carbon are from FAO estimates. An alternative carbon
price of $20/ton is substituted for the upper range estimate.
Appendix 1
List of the nine climate variables used in Maxent Species distribution modeling.
1.
RealMAT = Mean annual temperature (mean of monthly temperatures)
2. RealMAR = Mean annual precipitation (sum of mean monthly rainfall)
3. MinTemp = Mean temperature of the coldest month
4. MaxTemp = Mean temperature of the hottest month
5. MinPrec = Mean precipitation of the driest month
6. MaxPrec = Mean precipitation of the wettest month
7. ETPann = Annual total evapotranspiration.
First, monthly evapotranspiration rates ETPm (where m = values from 1 to 12
indicating calendar month) were calculated using the Thornthwaite equation
(http://leu.irnase.csic.es/microlei/manaul2/cdbm/cdbm2e.html):
ETPm = 16 x Nm ((10x Tm)/I)a
Where Tm = mean temperature for month m
Nm = monthly adjustment factor relating to the number of hours of daylight
I = Sum(Tm/5)1.514
a = 6.75 X 10-7 x I3 –7.71 x 10-5 x I2 + 1.792 X 10-2 x I + 0.49239
Annual total evapotranspiration (ETPann) was calculated by summing the 12
monthly evapotranspiration rates.
8. WBann = Annual water balance (mm)
WBann = RealMAR – ETPann
9. The number of months with a positive water balance (integer value between 1
and 12)