Myanmar Protected Areas: Context, Current Status ... - Istituto Oikos

Evergreen Forest
Typical vegetation of the central Rakhine Yoma, these forests are located mainly in the mountainous
regions of the study area, covering around 19% of the total. The dominant trees are Dipterocarpus spp.,
but also examples of Swintonia floribunda (Taung Theyet), Michelia champaca (Sagawa) and Mesua
ferrea (Gangaw) have been found. Some scattered deciduous trees are present, like Xylia dolabriformis,
Lannea grandis and Lagerstromea speciosa. The lower storey is rich in many species, mainly evergreen
and bamboos like Melocanna bambusoides (Kayin-Wa). The main threats are timber exploitation and
shifting cultivation that are causing a dangerous fragmentation and encroachment of this habitat. The
overall status of the remaining patches of forests seems to be still good.
Sparse Semi-evergreen Forest
The identification of this class turned out to be the most difficult due to the high habitat fragmentation.
This situation comprises a deeply intermixed mosaic of evergreen trees and deciduous trees, as scattered
big examples or small plots, and pure patches of Melocanna bambusoides, with different percentages of
composition. The process that has led to the creation of this vegetation seems generally the introduction
of Melocanna bambusoides in the evergreen and semi-evergreen forests, and then the establishment of
this aggressive species as pure patches. Totally this class comprises about 22% of the surface.
Bamboo Brakes
Other typical vegetation of the area, this class covers around 15% of the study area and is dominated
by Melocanna bambusoides, accompanied by scattered deciduous or evergreen individual trees. This
intrusive species has been signaled since 1956 (Chein Hoe 1956) and has the potential to spread to and
substitute many other forest types. As the dense growth of this bamboo precludes natural regeneration
of most species, the tendency is to produce pure plots of Melocanna bambusoides. The flowering of this
species occurs in mass after 30-40 years, and then they all wither and die. Other bamboo species present
in the region are Dendrocalamus longispatus (Talagu Wa), Gigantochloa macrostachya (Wa Pyu Gyi) and
Bambusa polymorpha.
Eastern dry deciduous forest and shrubs
Due to the low rainfall occurring on the eastern slopes, the vegetation is here formed entirely by
deciduous species. Generally the dominant layer is close but not dense, and there is a thick understorey
of bamboo (Dendrocalamus strictus or Hmyin Wa). The main trees found are Lannea grandis and Albizzia
procera (Sit). The area covered by this class is around 12% of the entire study area. Close to the road
many evidences of wood collection and over-exploitation have been observed, and the overall status
seems to decrease heading more and more to the lowest eastern slopes where the population density
is higher.
Plantation and degraded dry deciduous land
Moving towards the lowest slopes on the east side, the natural dry vegetation becomes highly
degraded by over-logging and forest fires. Remaining scattered patches of the so called Indaing forest
can be found: the main species present are Dipterocarpus obtusifolius (Inbo) and Dendrocalamus strictus.
Common in the area are large plantations of Tectona grandis, established in the last 2 to 3 years, or
other tree crops like cashew nuts. This class is covering around 13% of the total. Serious evidences of
soil erosion, in forms of both rills and gullies, are widely present. The habitat degradation due to human
over-exploitation of natural resources and modification on the natural vegetation cover is high.
Eastern Agricultural Areas
Differences from its western counterparts come from the diverse topographic location: the valley of the
Ayeyawaddy River. Due to the presence of extensive terraces of both alluvial and colluvial material, the
size of the farms is usually bigger, with a more homogenous distribution. Main crops are paddy rice,
both dry and irrigated, fruit trees, cotton, nuts, palms. The surface of this class is around 6% of the total.
Between the fields, some remaining patches of degraded dry deciduous forest are present.
DESCRIPTION OF VEGETATION COVER CHANGE
AND IDENTIFICATION OF MAIN CAUSES OF CHANGE
The overlapping of the land cover maps from 1974 and 2000/2003 has allowed to identify main changes
in the vegetation cover of the area.
The conversion from any type of natural vegetation to agriculture areas has been estimated at around
173 km² on the Ayeyawaddy valley and 92 Km² on the coastal side. This is consistent with the higher
rate of agricultural development possible in the lowlands close to the Ayeyawaddy River. An inverse
process, still to be analysed, has been the conversion of agricultural or degraded forest areas in mixed
deciduous forest: the surface involved has been estimated at 92 km². Also the conversion from Eastern
Dry Deciduous Forest to Plantation & Dry Degraded Forest is an indication of the high negative human
impact on the eastern slopes. This change has been noted in about 99 km². The lower rainfalls and worst
soil conditions could be enhancing the degradation process, giving to the vegetation fewer chances to
regenerate properly. The largest change has been identified however in the transformation from any
class to the Sparse Semi-Evergreen Forest or Bamboo Brakes (Table 17), evidence of the invasion of
Melocanna bambusoides in the area. More than 1,455 km² has been identified as being subject to this
trend. Although the Melocanna bambusoides is found naturally in the Rakhine Yoma Elephant Range WR,
it has been confirmed from this study that human practices in the area, like shifting cultivation and forest
fires, are a cause of first spreading of bamboo in new areas, where later it established itself as pure patches.
Vegetation class AREA
(Km2)
1974 2000
PERCENTAGE
of COVER
In-depth Study of Rakhine Yoma Elephant Range Wildlife Reserve
Vegetation class AREA
(Km2)
PERCENTAGE
of COVER
Bamboo brakes 455 27% Bamboo brakes 492 29%
Evergreen forest 913 54% Evergreen forest 508 30%
Sparse semi-evergreen
forest
320 19% Sparse semi-evergreen
forest
710 42%
Table 17 Main changes occurred in the vegetation cover classes from 1974 to 2000 in Rakhine Yoma
Elephant Range WR
140 141