Farming system changes in the Vietnamese uplands
– using fallow length and farmers’ adoption of
Sloping Agricultural Land Technologies as indicators of environmental sustainability
Rikke Folving & Henriette Christensen
Abstract
The environmental sustainability of the farming system changes
during the 1990s of two villages in the northwestern Vietnamese uplands was assessed by an analysis of changing fallow length practice and farmers’ adoption of Sloping Agricultural Land Technologies (SALT) in relation to slope steepness. The fallow length change
detection involved an identification of the vegetation succession
stage of the fallow vegetation at the time of clearance and was
based on high resolution satellite image classifications. The use of
SALT was surveyed by ground registration and overlaid with a digital elevation model. The results were coupled with an assessment
of farmers’ ability and willingness to adopt SALT in order to detect
changes in attitude and perceptions amongst the farmers regarding
their future agricultural strategies, and a discussion of the level of
livelihood diversification in the villages. The study illustrates the
complexity of the development situation in the Vietnamese uplands
and emphasises the importance of locally adapted development
strategies, suited to the traditional farming systems of the ethnic upland communities. The methodology for the analysis of changes in
fallow length based on satellite images offers promising potential
for the use of remote sensing technology in the assessment of environmental sustainability of shifting cultivation systems under
change.
In the Vietnamese uplands a development characterised
by rapid population growth, rural poverty, shortening of
fallow periods of the traditional shifting cultivation system, and forest degradation has taken place which has
been described by scholars as a “deepening environmental and social crisis” (Jamieson et al., 1998, pp 3; Cuc &
Rambo, 2001). During the last decades, governmental
programmes for upland development have been implemented in order to control environmental degradation and
ensure sustainable livelihoods, bringing about dramatic
changes in the traditional farming systems in the uplands
(Castella et al., 2006; Sikor & Truong, 2002; Müller &
Zeller, 2002). Vietnamese policy makers generally consider shifting cultivation systems damaging to the environment by causing deforestation and soil erosion, despite
the controversy regarding this argument (Fox, 2000;
Thrupp et al., 1997; Sam, 1994). An important scope of
these governmental programmes, in particular the nationwide land allocation programme effectuated by Resolu-
tion 10 in 1988 and the Land Law of 1993, has therefore
been to eliminate shifting cultivation by allocating fixed
fields to shifting cultivators and encouraging them to cultivate these permanently (Castella et al., 2006; Sowerine,
2004; Socialist Republic of Vietnam, 2002; Gomiero et al.,
2000; Quy, 1998). The shifting cultivation system relies
on a natural regeneration of soil fertility by shifting the location of the cultivated fields from year to year, leaving
the previously cultivated fields in fallow. The relationship
between the duration of the fallow period and the level of
soil fertility has been debated (Bruun et al., 2006; Mertz,
2002; Szott & Palm, 1996; Roder et al., 1995 and 1997).
Findings indicate that it is difficult to identify rigid relationships between the level of soil fertility and length of
fallow (Mertz, 2002). Nevertheless it is generally acknowledged that if the fallow period is substantially shortened, this mechanism of natural nutrient accumulation
must eventually be substituted for by other means of maintaining soil fertility, for example soil conservation meas-
Keywords
Fallow length, change detection, ethnic upland communities, livelihood diversification, shifting cultivation.
Rikke Folving (corresponding author)
Henriette Christensen
Department of Geography and Geology, University of Copenhagen,
Øster Voldgade 10, DK-1350 Copenhagen K, Denmark
E-mail: [email protected]
Geografisk Tidsskrift
Danish Journal of Geography 107(1):43-58, 2007
Geografisk Tidsskrift, Danish Journal of Geography 107(1) 43
Figure 1: Location of
study area.
ures (Fagerström et al., 2001 and 2002; Ruthenberg 1980;
Boserup 1965). The Vietnamese government’s upland development programmes have almost entirely focussed on
introducing intensive paddy cultivation in the valleys of
the upland region and less so on improving the traditional
farming system. However, the potential for intensive
paddy cultivation is limited in the uplands by steep topography and the large labour requirements for the construction of terraces and irrigation systems. Often knowhow is lacking among those ethnic minority groups who
do not have a tradition for paddy cultivation. These upland development programmes have therefore been criticised by various scholars for being poorly tailored to fit
the special conditions of the traditional farming systems
in the uplands (Fox et al., 2000; Fox, 2000). Sloping Agricultural Land Technologies (SALT) is an agroforestry
system developed for sustainable intensification of agricultural production on sloping lands and has become
widespread in many parts of the uplands of Southeast Asia
(Palmer et al., 1999; ICIMOD, 1999). SALT aims at erosion control, improvement of soil fertility, and provision
of adequate food and income for farmers (Palmer et al.,
1999). Various internationally funded development projects in the Vietnamese uplands have implemented SALT
in order to assist the government’s upland development
programmes (Peters, 2001; SFDP, 1998).
This study aims at investigating the farming system
changes taking place in the Vietnamese uplands and as-
44 Geografisk Tidsskrift, Danish Journal of Geography 107(1)
sessing the environmental sustainability of these changes.
The paper builds on a case study of two communities in
the northwestern Vietnamese uplands and suggests a
methodology for analysing the farming system changes
currently taking place in the uplands. It asks whether these
changes occurring during the 1990s indicate an environmentally sustainable development path, where shortening
of the fallow period is substituted by the adoption of
SALT. The assessment involves a land cover change detection analysis based on high resolution satellite images
used to identify changes in fallow length and a composite
mapping overlay of SALT. The results were coupled with
an assessment of farmers’ ability and willingness to adopt
SALT in order to detect changes in attitude and perceptions amongst the farmers regarding their future agricultural strategies, and a discussion of the level of livelihood
diversification in the villages.
Presentation of the study area
The two villages, Lem village in the commune of Huy Tan
and Bua Da village in the commune of Bac Phong, are situated approximately 150 km west of Hanoi, in Son La
Province, Phu Yen District (Figure 1).
The landscape in the region is characterised by steep
hills intersected by flat river valleys. The topography
ranges from the lowland of the river plains about 160 m
Table 1: Overview of village characteristics.
a.s.l. up to 1175 m a.s.l. at the top of the hill ranges. Soil
texture varies greatly between hill slopes and valley
floors. Fertile alluvial soils prevail on the valley floors
whereas most of the soils on hillslopes can be classified as
either red, loamy Ferrasols, or yellow Leptosols, according to the FAO Soil Taxonomy. These soils are generally
highly acidic, poor in nutrients and susceptible to erosion
(Wezel et al., 2002).
The two villages diverge from each other in terms of
ethnic composition, traditional farming system, market
access and population density (Table 1).
Lem village is inhabited by Thai and Muong ethnic
minorities mixed throughout generations and is situated
about five km from the district town of Phu Yen, ensuring
good market access, health service access and schooling.
The majority of the villagers are fluent in Vietnamese.
Bua Da village, which is inhabited entirely by the Dao
ethnic minority, is only accessible by foot. Travel time
from the district town is 90 minutes by car, 30 minutes by
motorboat and a one-hour walk from the shore of the Da
River, limiting access to market, health care and secondary schooling (see Figure 1). Villagers speak their ethnic
language and only few are fluent in Vietnamese, namely,
the village male leaders. In 1994 the illiteracy rate for Bua
Da village was 80% (CARE, 1994). Lem village comprised a total of 105 households and had a population density of 109 persons/km2 in 2000 and Bua Da village, a total of 43 households with a population density of 62 persons/km2. The farmers in Lem Village traditionally manage their land according to a type of farming system
termed composite swiddening, in which shifting cultivation represents an integral component (Rambo, 1998;
Vien, 1998). In addition to shifting cultivation fields on
the slopes, the farming system involves home gardens
close to the homestead planted with fruit trees and vegetables, paddy cultivation and fishponds in the valleys, as
well as animal husbandry. The high level of market integration is manifested by the extent of income-generating
activities, such as the sale of cash crops and animal husbandry. The farming system is more diversified than in
Bua Da village, where farmers rely on a traditional shifting cultivation system. In Bua Da village the cultivation of
paddy is very limited and home gardens and animal husbandry only play a minor role in the farming system.
An integrated rural development project was initiated
within the villages in 1994 by an international non-governmental organisation (NGO). The NGO project promoted a move away from a reliance on shifting cultivation
towards a diversification strategy of the farming system
and encouraged farmers to adopt SALT. SALT had the
dual purpose of protecting the land from soil erosion and
improving and diversifying production through bench terraces, hedgerows, fruit and timber tree planting and intercropping with perennials. Farmers were offered loans for
the start-up, covering the cost of construction materials
and seedlings, and received training through courses and
model farms. Additional project activities included the introduction of alternative income-generating activities,
such as cultivation of marketable high-yield crop varieties, fish ponds and animal husbandry.
The governmental land allocation programme was initiated in 1994 and finalised in 1996 when households received formal land use certificates. Both villages traditionally had well-defined systems of customary tenure
regulations, which defined land use rights among families
and lineages. In Bua Da village, customary land use rights
to land which had not formally been allocated were still
recognised among the villagers, whereas in Lem village,
land had been restricted for a long period due to the high
population density and farmers were allocated most of the
land which originally belonged to them.
Method
Data collection
The assessment of the environmental sustainability of the
farming system changes involved a retrospective and a
forecasting perspective, using data from fieldwork con-
Geografisk Tidsskrift, Danish Journal of Geography 107(1) 45
Table 2: List of satellite data used to study the
two villages.
ducted in the autumn of 2000. The retrospective perspective was based on historical back-tracking by a fallow
length change detection analysis based on high resolution
satellite image classifications and GIS analysis, coupled
with interviews with farmers about their land use practices in the past. The use of SALT was surveyed by
ground registration using a hand-held GPS (Global Positioning System) and overlaid with the result of the fallow
clearance analysis and with a digital elevation model in
order to evaluate the implementation of SALT in relation
to the steepness of the upland. The forecasting perspective focused on an examination of farmers’ ability and
willingness to implement SALT, an assessment of their
future agricultural strategies and the level of livelihood
diversification in each village. Information on land use
practices was collected by a questionnaire survey, field
visits and semi-structured interviews with farmers and
other key informants, such as governmental institution
personnel on the district level and staff from the NGO
project. 20 semi-structured household interviews were
conducted, 12 in Lem village and 8 in Bua Da village, and
a questionnaire survey was carried out with 30 households in Lem village. No questionnaire survey was conducted in Bua Da village because of restrictions imposed
on the length of the authors’ stay in the village. Information was collected on the history of land cover and land
use, fallow length, use of SALT, accessibility to fields,
animal husbandry, and income generating activities as
well as future plans. Village borders were mapped during
transect walks with village members. All household and
field data were georeferenced in a GIS database in ArcView, containing satellite image derived land cover
maps and digital elevation models based on topographical maps on the scale 1:50 000 with 20, occasionally 10,
metre contour intervals. The positional accuracy of the
GPS registrations was a minimum of 10 metres for the
ground truthing points used for the land cover classifications and occasionally up to 20 metres for the SALT and
46 Geografisk Tidsskrift, Danish Journal of Geography 107(1)
village border registrations, mainly due to poor satellite
coverage at the time of fieldwork.
Land cover classification
The land cover was determined by classifying two Landsat Thematic Mapper (TM) satellite images from 1992
and 1993, and two enhanced TM (ETM+) images from
1999 and 2000 (Table 2).
The images were geometrically rectified to the 1999
ETM+ image in UTM coordinates and Datum WGS 84,
using an image-to-image rectification method with 30
ground control points and an RMS error of less than one
pixel. The spatial resolution of the Landsat images is 30
metres, which makes it too coarse to adequately depict individual fields of less than one hectare and any of the
SALT within the area. Households, nevertheless, usually
clear and cultivate larger patches of land adjacent to one
another, which helps make the image data useful for land
cover mapping despite the mismatch in spatial resolution.
The spectral resolution of the Landsat TM and ETM+ is
likewise coarse for the type of heterogeneous landscape
typically found in shifting cultivation landscapes characterised by various vegetation succession stages of fallowed land, and the spectral signature of land cover
classes often overlap (Tottrup, 2002). As a result, a corresponding coarse land cover classification was used, dividing the land cover into four broad land use and land cover
classes (Table 3).
All images were classified according to the maximum
likelihood classification algorithm. Ground control points
collected during the fieldwork in autumn 2000 were used
for generating training sets for the major land cover
classes found in the area and used for the 2000 image classification. All images were recorded in the autumn, between the end of October and December, in order to increase the likelihood of post-harvest registration. The
1992 and 2000 images were recorded in late October and
early November, respectively, when upland rice is some-
Table 3: Description of the major land cover classes within the
study area.
times still maturing on the fields. In order to include these
fields in the shifting cultivation fields class, training sets
were included for both cleared upland fields and vegetated
upland fields when they could be identified. The spectral
signature of the land use classes was used to classify the
historical images. An automated radiometric normalisation was attempted in order to exclude the effects of variations in non-surface factors, such as atmospheric conditions, earth-sun distance and sun angle, on the brightness
values of the images but proved unsuccessful (Heo and
FizHugh, 2000; Eckhardt et al. 1990). As an alternative,
training sets for the historical images were manually detected by visual interpretation and compared with the
spectral signature for the 2000 image. A Jeffries-Matusita
(JM) distance separability analysis was used to assess the
spectral separability between the land cover classes for
each classification and generally revealed acceptable results. Low separability values between the shifting cultivation fields class and the shrub and grass class for 1999
and 2000 (0.641 in 1999 and 0.526 in 2000 for Lem village and 0.478 in 2000 for Bua Da village) was the only
problem. This may be explained by the spectral signature
similarity between stubble left on the field after harvest
and young grass fallow for the 1999 image, and between
mature rice and maize plants on the one hand and grass on
the other, for the 2000 image. The overall classification
accuracy from the confusion error matrices based on the
training sets was between 85.63% and 97.34%, as reported in Table 4. The resulting land cover maps were
used as a basis for the fallow clearance analysis.
Fallow length assessment
The prevalent type of fallow vegetation cleared for shifting cultivation is used as an indication of fallow length
practice within the villages. Succession studies in shifting
cultivation environments involve strong elements of unpredictability as different vegetation species have different effects on the level of soil fertility restoration during
the fallow regrowth (Roder et al., 1995 and 1997; Szott &
Palm, 1996; Aweto, 1985; Ramakrishnan and Toky 1981).
Leisz (2001) investigated the vegetation succession and
associated soil fertility in the neighbouring Hoa Binh
Table 4: Overall classification accuracy results based on training sets
confusion matrices.
Geografisk Tidsskrift, Danish Journal of Geography 107(1) 47
Province and suggested a natural vegetation succession
during the fallow period evolving from herbaceous to either shrub-based or tree-based fallow vegetation. During
the first two-three years after abandonment several
species of long grass evolve on the field. Different successions are likely to occur during the following threefive years of the fallow period. The vegetation may develop into a shrub community dominated by Eupatorium
odoratum, indicating a climax situation on a relatively
low fertility status, thus representing an insufficient nutrient regeneration and a degraded soil (Vidal, 1997; Ramakrishnan and Toky 1981). Otherwise, the grass vegetation gradually evolves into an evergreen bush community,
which subsequently develops into an older bush forest, at
some stage between six-fifteen years after abandonment,
after which a secondary forest cover is established. Secondary forest, as opposed to a fallow dominated by shrub
and grass species, is the vegetation type with the best ability to restore soil fertility (Leisz 2001; Vien, 1998; Ramakrishnan and Toky 1981). This succession development is classified into the following simplified scenarios
for fallow vegetation succession within the study area
(Figure 2).
The prevalent type of fallow vegetation cleared for
shifting cultivation is identified by locating active shifting cultivation fields in 1993 and 2000 and back-tracking
the location of these fields to find the type of fallow vegetation cleared the previous year. Based on the vegetation
succession scenarios outlined above, the clearance of forest and bush indicates a long fallow practice and is interpreted as sufficient natural regeneration of soil fertility,
whereas the clearance of shrub and grass indicates a short
fallow length and is interpreted as insufficient natural regeneration of soil fertility.
Figure 2: Fallow vegetation succession scenarios within
the study area.
48 Geografisk Tidsskrift, Danish Journal of Geography 107(1)
The spatial coincidence of SALT, short fallow and slope
steepness
The location of the SALT has been evaluated in relation to
the fallow practice and the steepness of the land. A spatial
coincidence of SALT and short fallow practice implies a
transition from maintaining soil fertility by the use of fallow, as in traditional shifting cultivation systems, towards
a more permanent type of cultivation in which soil fertility
is maintained by the use of SALT. As such, areas with a
combination of SALT and short fallow indicate an environmentally sustainable agricultural intensification
whereas areas of short fallow without SALT indicate an
unsustainable situation. Furthermore, as SALT works by
reducing erosion on sloping land, the location of SALT in
relation to slope steepness was included in the spatial overlay analysis. The steepness of the slope is a simple indicator of the overall soil erosion risk since this is determined
by a complex interplay of a series of factors, including
slope steepness and length, the inherent erodibility of the
soil, the erosivity of the rain and the protection offered by
plant cover (Laflen & Roose, 1998; Renard et al., 1991;
Wischmeier and Foster 1974; Wischmeier and Smith,
1965). The latter has received particular attention from researchers in Vietnam, who have investigated the effects of
the level of land cover fragmentation on soil erosion in the
Vietnamese uplands (Ziegler et al., 2004 and 2006).
Results
Land cover classifications
The results of the land cover classifications show that Bua
Da village experienced a decrease in forest and bush cover
and an increase in the active shifting cultivation area during the 1990s, whereas the land cover in Lem village remained largely unchanged, except for the proportion of
the area under active shifting cultivation, which has doubled between 1992 and 2000 (Figures 3-4). The increase
in the area of shifting cultivation fields in Bua Da village
was more than three fold between 1992 and 2000.
Qualitative accuracy assessment of the land cover classification results
It is likely that classification inaccuracy accounts for part
of the explanation for the small area of shifting cultivation
fields classified in Bua Da village in 1992. The image was
recorded in late October when some fields had not yet
been harvested, but these fields could not be visually identified on the image and therefore the class was based on
Figure 3: Land cover classification results (area in ha).
Figure 4: Land cover classification results (in percentage of
total village area).
training sets of cleared fields only. This was not the case
for Lem village, where the shifting cultivation class contained both pre- and post-harvested fields. Likewise, the
large area of shifting cultivation fields in 2000 in both villages may be due to the inclusion of training sets of both
cleared and mature fields, causing a spectral overlap with
the shrub and grass class.
Other classification problems become evident when the
land cover maps are analysed visually in spite of the fact that
the separability analysis and the overall accuracy assessment of the classifications were acceptable, see Figures 5-6.
A land cover change from the forest and bush class to
the shrub and grass class is impossible during a one-year
time span. A shifting cultivation cycle with clearance, cultivation, abandonment and regrowth would be necessary
and cannot be undertaken within a single year. In addition,
paddy fields are classified as shifting cultivation fields,
mainly in Lem village, and vice versa in Bua Da village.
The paddy field area is small and fragmented in Bua Da
village and fields are only cultivated once per season,
making it difficult to adequately incorporate them in the
classification.
Assuming that all land within the villages except
paddy fields is part of the shifting cultivation cycle, the
land cover in the early 1990s indicates a low intensity
shifting cultivation system based on a long fallow period
in Bua Da and a higher intensity shifting cultivation system based on a combination of mainly short fallow periods and some long fallow practice in Lem village. By the
end of the 1990s, the two villages have a similar land
cover: Bua Da has undergone an intensification of the
shifting cultivation system with a shift to a short fallow
Geografisk Tidsskrift, Danish Journal of Geography 107(1) 49
Figure 5: Land cover in Bua Da village.
Figure 6: Land cover in Lem village.
practice and assuming that the shifting cultivation area is
exaggerated in 2000 due to classification inaccuracies,
Lem village has retained its level of cultivation intensity.
However, not all the village land is part of the shifting
cultivation cycle; in particular, some forest land is protected by law and used as community forest for the collection of non-timber forest products and hunting, making a fallow length assessment by a fallow clearance
analysis a more accurate assessment.
doubled. The proportion of shifting cultivation fields cultivated in consecutive years increased from 4% in 1993 to
constituting 18% of the shifting cultivation area in 2000.
7 ha, equivalent to 5% of the shifting cultivation area in
Bua Da in 2000, was covered by clouds in 1999 and omitted from the fallow clearance analysis. The class depicting
shifting cultivation fields classified as paddy fields the
previous year is considered to consist of wrongly classified areas and was likewise omitted from the analysis.
These results confirm that Bua Da village has undergone
an intensification of the shifting cultivation system with a
shift to a short fallow practice during the 1990s. However,
a comparison of the fallow clearance practice in 2000 between Lem and Bua Da villages reveals that in relative
terms, the proportion of cleared forest and bush, indicating long fallow, was three times greater in Bua Da village.
The relative proportion of shifting cultivation fields cultivated consecutive years was likewise twice as large for
Lem village and these findings suggest that despite the
similarities in actual land cover between the villages, the
cultivation system in Lem village is more intensive than in
Bua Da village.
The results of the fallow clearance analysis were corroborated by the interviews with the farmers about their
fallow practice. The majority of the farmers in both vil-
Fallow clearance
The results of the fallow clearance analysis confirm that
the fallow length practice in Lem village has not changed
substantially (Figures 7-8).
The relative proportion of forest and bush fallow indicating long fallow practice has increased from constituting 4% of the shifting cultivation area in 1993 to 11% in
2000 and the proportion of shrub and grass fallow cleared
as well as the proportion of shifting cultivation fields cultivated in consecutive years remained more or less constant. In Bua Da village a more extreme change has taken
place. The relative proportion of cleared forest and bush
fallow indicating long fallow practice decreased from
66% to 32%, whereas the proportion of shrub and grass
fallow cleared, indicating a short fallow practice, almost
50 Geografisk Tidsskrift, Danish Journal of Geography 107(1)
Figure 7: Fallow
length change detection results (area
in ha).
Figure 8: Fallow
length change detection results (in percentage of total shifting cultivation area
in the respective year
of analysis).
lages reported that the fallow vegetation at clearance time
in 2000 predominantly consisted of grass species and
shrub vegetation, indicating a short fallow practice. The
average fallow length in Lem village was two years and in
Bua Da village farmers reported an average four-year fallow period. In Lem village 40% the farmers reported letting their land lie fallow for less than a year, a practice
brought about by the introduction of soybean by the NGO
project in 1997. This short fallow lasted two-four months,
depending on crop rotations involving maize and soybean.
It was described by the farmers as an alternative to the traditional fallow practice for sustaining soil fertility by leaving crop residues from the nitrogen-fixating soybean on
the field.
Implementation of SALT
SALT are most abundant and best incorporated into the
farming system in Lem village, where they were observed
Geografisk Tidsskrift, Danish Journal of Geography 107(1) 51
Table 5: Combinations of SALT implemented (in percentage of surveyed fields).
or reported on 56% of the surveyed fields as opposed to
31% in Bua Da village (Table 5).
All of the interviewed farmers in Lem village have implemented at least one type of SALT and mostly various
types were used on the same field. Few farmers reported
the use of SALT in Bua Da village, and if they did, only
one type was used per field. Tree planting, alone and in
combination with intercropping, was the most common
type of SALT implemented in both villages. Timber trees
are typically planted on the upland shifting cultivation
fields, and fruit trees in home gardens close to the homesteads. Hedgerows are to a lesser degree planted in both
villages, mainly in the upland fields, whereas a few terraces were observed or reported in Lem village only, typically in home gardens.
The spatial coincidence of SALT, short fallow and slope
steepness
25 of the 38 surveyed fields with SALT were geo-referenced in Lem village and 14 of the 19 surveyed fields
with SALT in Bua Da village. Figures 9 and 10 show
these geo-referenced SALT overlaid with the fallow
clearance results for 2000.
SALT in Lem village were mostly implemented on
fields with short fallow practice and fields cultivated in
consecutive years. Some SALT were found in areas
which have not been cultivated in 2000, revealing the fact
52 Geografisk Tidsskrift, Danish Journal of Geography 107(1)
that land is still left fallow after the implementation of
SALT. In Bua Da village, most SALT is implemented on
fallowed land and a few tree planting areas on cleared forest and bush fallow. Only few SALT have been implemented on fields with short fallow practice.
For both villages a majority of the geo-referenced
fields with SALT were located on steep land potentially in
need of erosion protection. More than half of the geo-referenced fields with SALT in Lem village were on land
with a slope steepness of between 25-40°. These SALT
constituted some labour intensive types such as bench terraces and hedgerows but mostly tree planting and intercropping. The remaining geo-referenced fields with SALT
were on land with a slope of below 25°. Three of these
were on relatively flat land and were in fact home gardens
with fruit trees, some in combination with bench terracing
and intercropping. Land with a slope steeper than 40° was
generally not cultivated in Lem village. In Bua Da village
all the geo-referenced fields with SALT were located on
land with a slope steeper than 10°. Most tree planting was
on a 25-40° slope whereas the three geo-referenced fields
with hedgerows were located on land with a slope of between 10-25°. All the fields with SALT were close to the
residential area.
Willingness and ability to implement SALT
Information from the semi-structured interviews from both
Figure 9: Slope steepness and
SALT in 2000.
villages and the questionnaire survey from Lem village
was used to assess farmers’ ability and willingness to implement SALT, their future agricultural strategies as well
as the level of livelihood diversification in the villages.
In Lem village, an on-going diversification of the
farming system was taking place, in which shifting cultivation in the upland was one of a range of farming activities. Animal husbandry, cultivation of marketable high
yielding maize and soybeans from permanent fields, and
tree planting were important elements of the majority of
the farmers’ livelihood strategies. Most farmers expressed
their interest in implementing SALT, particularly fruit
trees (57%), bench terraces (47%) and hedgerows (20%)
in their near future agricultural strategies. However, despite this enthusiasm farmers were also critical towards
the implementation of SALT. They stated that the con-
struction of bench terraces was impeded by the fact that it
was too expensive, demanded too much land and labour
and was too complicated (Table 6).
Lack of land was the main obstacle stated for
hedgerows and the reason given was that the hedgerows
Table 6: Farmers’ opinion about limiting factors for construction
of bench terrace and hedgerow planting in Lem village.
Geografisk Tidsskrift, Danish Journal of Geography 107(1) 53
Figure 10: Fallow length and
SALT in 2000.
took up land and shaded the surrounding crops. Secured
land ownership was mentioned as an incitement for investment in the land during semi-structured interviews.
The governmental land allocation had generally been
welcomed by the farmers. Due to the high population
density land had been restricted for a long period and the
granting of formal land use rights, which allowed for legal inheritance of land, encouraged farmers to plan in a
long-term perspective. Generally farmers expressed reluctance to construct and maintain labour-intensive SALT
far away from their homestead because it involved spending extra time going back and forth to the fields. Newly
established households were generally reluctant to engage in SALT because they lacked capital for investment
and did not see themselves in a position to cope with the
54 Geografisk Tidsskrift, Danish Journal of Geography 107(1)
risk of engaging in the loans provided by the NGO project. Older households and newly established households
where the children were too young to contribute to the
work force were generally unable to provide the necessary
labour to construct terraces. Generally more farmers in
Lem village were able to overcome the constraints involved in implementing new agricultural strategies than in
Bua Da village. This was because the higher degree of income-generating activities made more capital available to
the farmers, who were, for example, able to implement
terraces by hiring labour for their construction.
In Bua Da Village, there were limited indications of a
near future agricultural diversification. Generally the
farmers were more sceptical towards SALT and did not
plan to implement SALT in the near future, except for fruit
trees. The few farmers in Bua Da village who were applying SALT were among the wealthiest and best educated
and they had participated in a training course held by the
NGO project. Several of the farmers did however express
concerns of soil erosion and decreasing yields in their uplands due to the decreasing fallow periods and stated that
alternative income strategies, such as fruit tree planting
and animal husbandry, would be important future agricultural strategies. The land allocation was mostly perceived
as a freedom constraining factor, limiting the traditional
shifting cultivation practice and was not associated with
improved land tenure security: “Before the land allocation in 1996 it was possible to leave the land fallowed for
long periods – now the land can only rest for a short period. In our opinion tenure security has not changed after
the land allocation” (Farmer from Bua Da village during
focussed group interview). The main problem as stated by
the farmers was their limited market access. Farmers experienced problems in selling their fruits and pigs, which
were not only related to the lack of physical infrastructure.
Market access was also impeded by the language barrier
and cultural difference between them and the neighbouring villages and the district town, which reinforced a sense
of social remoteness. The villagers expressed a strong
awareness of belonging to an ethnic minority isolated
from Vietnamese society and a general perception of lack
of acceptance by the outside world.
Discussion and conclusions
The study has shown that in 2000 a short fallow practice
prevailed in both villages. For Lem village, the situation
was almost identical to 1993, whereas Bua Da village has
undergone an intensification of the shifting cultivation
system with a shift from a predominantly long fallow system involving the clearance of forest and bush in 1993 to
a combined forest and bush, and shrub and grass fallow
system in 2000. In Lem village, the use of short fallow
was combined with SALT in 2000, whereas in Bua Da village only few SALT have been implemented on short fallow fields. In both villages SALT have generally been implemented on the steep upland most prone to erosion,
though SALT is also concentrated close to the residential
areas due to labour constraints in connection with travel
time. In Lem village this development illustrated a change
towards a more permanent type of cultivation in which
soil fertility is maintained by SALT, whereas for Bua Da
village, the change illustrated a shortening of the fallow
period which has not been effectively compensated for by
the application of SALT.
The ability and willingness of farmers to implement
SALT varied between the villages as well as between
households within the villages due to factors such as differences in household composition affecting work availability and consumption needs, wealth status, level of education, and distance to upland fields. In both villages it is
the resourceful and innovative farmers who are most interested in SALT, whereas newly established households and
households where the members are old lack either the capital or labour force necessary to apply SALT. In Lem village, a composite swidden farming system was being used,
which seemed compatible with SALT, and the farmers
generally expressed a positive attitude towards adopting
SALT. In Bua Da village the implementation of SALT was
not as successful. The traditional shifting cultivation system still played the major role in the farming system and
farmers did not plan to focus on SALT in the near future.
The study illustrates the complexity of the farming
systems in the Vietnamese uplands and emphasises the
importance of locally adapted development strategies
aimed at controlling environmental degradation. For Bua
Da village a more appropriate development intervention
would be to focus on the potential for developing the traditional shifting cultivation system, for example, by investigating the potential for improved fallow (Sanchez,
1999; Szott & Palm, 1996).
The methodology tested in this study for analysing fallow clearance by use of satellite images offers promising
potential for the use of remote sensing technology in the
assessment of environmental sustainability of shifting
cultivation systems under change. The inherent problem
of spatial resolution in this study could be solved by the
application of satellite images with a finer spatial resolution, such as SPOT and ASTA. Furthermore, the registration of the SALT by GPS requires time-consuming fieldwork but would be possible using aerial photographs,
given that they were available. In addition, the separability between the land cover classes could be improved by
incorporating seasonal variability into the analysis. By
working with two images from different seasons it may be
possible to detect changes in plant phenology over time,
thereby enhancing the separability between the classes
(Tottrup, 2004; Hill and Foody, 1994). Solving the inaccuracies related to the establishment of a more detailed
vegetation succession and associating it with soil fertility
is a far more complicated issue which is not attainable
through the use of remotely sensed data.
Geografisk Tidsskrift, Danish Journal of Geography 107(1) 55
Acknowledgements
The authors wish to acknowledge two anonymous reviewers for valuable comments and thank the farmers of
Bua Da and Lem village for participation in the research.
The Danish Network for Agricultural Research and Development are acknowledged for financial support and
CARE Denmark and CARE Vietnam for logistic support.
References
Aweto, A.O. (1985): Organic Matter and Nutrient Content of Soils under four Types of Bush Fallow Vegetation in SW Nigeria. GeoJournal 10(4): 409-415.
Boserup, E. (1965): The conditions of agricultural
growth. The economics of agrarian change under population pressure. London. Earthscan Publications
Limited.
Bruun, T. B., Mertz, O. & Elberling, B. (2006): Linking
yields of upland rice in shifting cultivation to fallow
length and soil properties. Agriculture, Ecosystems
and Environment 113: 139-149.
CARE (1994): Phu Yen Natural resources and Community Development Project. Baseline PRA for Muong
Thai, Bac Phong and Tan Phong Communes, Phu Yen
District, Son La Province. Hanoi, CARE Vietnam internal project document.
Castella, J. C., Boissau, S., Thanh, N. H. & Novosad, P.
(2006): Impact of forestland allocation on land use in
a mountainous province of Vietnam. Land Use Policy
23: 147-160.
Cuc, L. T. & Rambo, A.T. (2001): Bright Peaks, Dark Valleys: A Comparative Analysis of Environmental and
Social Conditions and Development Trends in Five
Communities in Vietnam's Northern Mountains.
Hanoi, National Publishing House.
Eckhardt, D. W., Verdin, J. P. & Lyford, G .R. (1990): Automated Update of an Irrigated Lands GIS Using
SPOT HRV Imagery. Photogrammetric Engineering &
Remote Sensing 56(11): 1515-1522.
Fagerström, M. H. H., van Noordwijk, M., Phien, T. &
Vinh, N. C. (2001): Innovations within upland ricebased systems in northern Vietnam with Tephrosia
candida as fallow species, hedgerow, or mulch: net return and farmers’ response. Agriculture, Ecosystems
and Environment 86: 23-37.
Fagerström, M. H. H., Nilsson, S. I., van Noordwijk, M.,
56 Geografisk Tidsskrift, Danish Journal of Geography 107(1)
Phien, T., Olsson, M., Hansson, A. & Svensson, C.
(2002): Does Tephrosia candida as fallow species,
hedgerow or mulch improve nutrient cycling and prevent nutrient losses by erosion on slopes in northern
Viet Nam? Agriculture, Ecosystems and Environment
90: 291-304.
Fox, J. (2000): How Blaming ‘Slash and Burn’ Farmers is
Deforesting Mainland Southeast Asia. Honolulu, EastWest Center, Asia Pacific Issues 47.
Fox, J., Truong, D. M., Rambo, A. T., Tuyen, N. P., Cuc,
L. T. & Leisz, S. (2000): Shifting Cultivation: A New
Old Paradigm for Managing Tropical Forests. Bioscience 50(6): 521-528.
Gomiero, T, Pettenella, D., Trieu, G. P. & Paoletti, M. G.
(2000): Vietnamese Uplands: Environmental and Socio-economic Perspective of Forest Land Allocation
and Deforestation Process. Environment, Development and Sustainability 2: 119-142.
Heo, J. & FitzHugh, T. W. (2000): A Standardized Radiometric Normalisation Method for Change Detection
Using Remotely Sensed Imagery. Photogrammetric
Engineering & Remote Sensing 66(2): 173-182.
Hill, R. A., & Foody, G. M. (1994): Separability of tropical rain-forest types in the Tambopata-Candamo reserved zone, Peru. International Journal of Remote
Sensing 15(13): 2687-2693.
International Center for Integrated Mountain Development (ICIMOD). WWW.ICIMOD.org.
Jamieson, N. L., Cuc, T. C. & Rambo, A. T. (1998): The
Development Crisis in Vietnam’s Mountains. Honolulu, East-West Center Special Reports, 6.
Laflen, J. M. & Roose, E. J. (1998): Methodologies for
Assessment of Soil Degradation Due to Water Erosion.
Pp. 31-56 in: Lal, R., Blum, W.H., Valentine, C. &
Stewart, B.A. (eds.): Methods for Assessment of Soil
Degradation. New York, CRC Press.
Leisz, S., Troung, D. M., Chan, L. T. & Hai, L. T. (2001):
Land-cover and land use. Pp 85-122 in: Cuc, L. T. &
Rambo, A. T. (eds.): Bright Peaks, Dark Valleys: A
Comparative Analysis of Environmental and Social
Conditions and Development Trends in Five Communities in Vietnam's Northern Mountains. Hanoi, National Publishing House.
Mertz, O. (2002): The relationship between length of fallow and crop yields in shifting cultivation: a rethinking. Agroforestry Systems 55: 149-159.
Müller, D. & Zeller, M. (2002): Land use dynamics in the
central highlands of Vietnam: a spatial model combining village survey data with satellite imagery interpre-
tation. Agricultural Economics 27: 333-354.
Palmer, J. J., Guliban, E. & Tacio, H. (1999): Use and success of incentives for promoting Sloping Agricultural
Land Technology (SALT) in the Philippines. Pp. 309324 in: Sanders, W., Huszar, P.C., Sombatpanit, S. &
Enters, T. (eds.): Incentives in Soil Conservation. From
Theory to Practice. U.S.A., World Association of Soil
and Water Conservation, Science Publishers.
Peters, J. (2001): Transforming the “model” approach to
upland rural development in Vietnam. Agriculture and
Human Values 18: 403-412.
Ramakrishnan, P. S. & Toky, O. P. (1981): Soil Nutrient
Status of Hill Agro-ecosystems and Recovery Pattern
after Slash and Burn Agriculture (Jhum) in North-Eastern India. Plant and Soil 60: 41-64.
Rambo, A. T. (1998): The Composite Swiddening Agroecosystem of the Tay Ethnic Minority of the Northwestern Mountains of Vietnam. Pp. 43-86 in: Patanothai, A.
(ed.): Land Degradation and Agricultural Sustainability: Case Studies from Southeast and East Asia. Khon
Kaen, SUAN Regional Secretariat, Khon Kaen University.
Renard, K. G., Foster, G. R., Weesies, G. A. & Porter, J. P.
(1991): RUSLE - Revised universal soil loss equation.
Journal of Soil and Water Conservation 46: 30-33.
Roder, W., Phengchanh, S. & Keoboulapha, B. (1995):
The relationships between soil, fallow, weeds and rice
yields in slash-and-burn systems of Laos. Plant and
Soil 176: 27-36.
Roder, W., Phengchanh, S. & Maniphone, S. (1997): Dynamics of soil and vegetation during crop and fallow
period in slash-and-burn fields of northern Laos. Geoderma 76: 131-144.
Ruthenberg, H. (1980): Farming Systems in the Tropics.
Third edition. London, Oxford University Press.
Sam, D. D. (1994): Shifting Cultivation in Vietnam: Its
social, economic and environmental values relative to
alternative land use. London, International Institute for
Environment and Development (IIED), Forestry and
Land Use Series 3.
Sanchez, P. A. (1999): Improved fallows come of age in
the tropics. Agroforestry Systems 47: 3-12.
Sikor, T. & Truong, D. M. (2002): Agricultural Policy and
Land Use Changes in a Black Thai Commune of
Northern Vietnam, 1952-1997. Mountain Research
and development 22(3): 248-255.
Social Forestry Development Project (SFDP) (1998):
Land Use Planning & Land Allocation in Vietnam with
particular reference to improvement of its process in
the Social Forestry Development Project Song Da
(SFDP). Hanoi, GTZ Consultancy Report 16.
Socialist Republic of Vietnam (2002): The Comprehensive Poverty Reduction and Growth Strategy
(CPRGS). Hanoi, Socialist Republic of Vietnam.
Sowerine, J. C. (2004): Territorialisation and the Politics
of Highland Landscapes in Vietnam: Negotiating Property Relations in Policy, Meaning and Practice. Conservation & Society 2(1): 97-136.
Szott, L. T. & Palm, C. A. (1996): Nutrient stocks in managed and natural humid tropical fallows. Plant and Soil
186: 293-309.
Thrupp, L. A, Hecht, S. B., Browder, J. O., Lynch, O. J.,
Megateli, N. & O’Brian, W. (1997): The Diversity and
Dynamics of Shifting Cultivation: Myths, Realities,
and Policy Implications. Washington, D.C., World Resources Institute.
Tottrup, C. (2002): Deforestation in the upper Ca River
Basin in north central Vietnam – a remote sensing and
GIS perspective. Geographica Hafniensia C12, Institute of Geography, University of Copenhagen.
Tottrup, C. (2004): Improving tropical forest mapping using multi-date Landsat TM data and pre-classification
image smoothing. International Journal of Remote
Sensing 25(4): 717-730.
Vidal, E. J. (1997): Paysages végétaux et plantes de la
Péninsule indochinoise. Paris, Éditions KARTHALA,
Agence de la Francophonie (ACCT).
Vien, T. D. (1998): Soil Erosion and Nutrient Balance in
Swidden Fields of the Composite Swiddening Agroecosystem in the Northwestern Mountains of Vietnam.
Pp. 65-86 in: Patanothai, A. (ed.): Land Degradation
and Agricultural Sustainability: Case Studies from
Southeast and East Asia. Khon Kaen, SUAN Regional
Secretariat, Khon Kaen University.
Wezel, A., Luibrand, A. & Thanh, L. Q. (2002): Temporal
Changes of Resource Use, Soil fertility and Economic
Situation in Upland Northwest Vietnam. Land Degradation & Development 13(1): 33-44.
Wischmeier, W. H., & Smith, D. P. (1965): Predicting
Rainfall Erosion Losses from Cropland East of the
Rocky Mountains. Guide for Selection of Practices for
Soil and Water Conservations. U.S.A., Agricultural
Handbook No. 282, Agricultural Research Service,
U.S Department of Agriculture in Coorporation with
Purdue Agricultural Experiment Station.
Wischmeier, W. H. & Foster, G. R. (1974): Evaluating irregular slopes for soil loss prediction. Transactions of
ASAE 17: 305-397.
Geografisk Tidsskrift, Danish Journal of Geography 107(1) 57
Quy, V. (1998): An overview of the environmental problems in Vietnam. Vietnamese Studies 129(3): 7-32.
Ziegler, A. D., Giambelluca, T. W., Tran, L. T., Vana, T.
T., Nullet, M. A., Fox, J., Vien, T. D., Pinthong, J.,
Maxwell, J. F. & Evett, S. (2004): Hydrological consequences of landscape fragmentation in mountainous
northern Vietnam: evidence of accelerated overland
flow generation. Journal of Hydrology 287: 124-146.
Ziegler, A. D., Tran, L. T., Giambelluca, T. W., Sidle, R.
C., Sutherland, R. A., Nullet, M. A. & Vien, T. D.
(2006): Effective slope lengths for buffering hillslope
surface runoff in fragmented landscapes in northern
Vietnam. Forest Ecology and Management 224: 104118.
58 Geografisk Tidsskrift, Danish Journal of Geography 107(1)