identification and quantification forest degradation drivers in tropical dry forests: a case study...
DESCRIPTION
In Western Mexico, the area studied, shifting cultivation does not cause deforestation but does cause degradation and forest encroachment.TRANSCRIPT
Identification and quantification forest degradation drivers in tropical dry
forests: a case study in Western Mexico
- Technical session : “From understanding drivers to gaining leverage at the
tropical forest margins: 20 years of ASB Partnership”IUFRO XXIV World Congress, Salt Lake City, 5 -11 Oct 2014
Lucia Morales-Barquero, Armonia Borrego, Margaret Skutsch, Christoph Kleinn & John Healey.
Contents
• Introduction • Methods • Research Approach• Results & Discussion• Conclusions and Significance
Introduction• Tropical Dry Forests (TDFs) and REDD+: – TDFs have been neglected in REDD+ because of low
carbon content and small annual increments– Nonetheless TDFs cover approx 42% of tropical and
subtropical forest areas– Many are quite degraded – Hold relatively high population
densities of forest depenent people
• TDFs and forest degradation processes: – Commonly used for shifting cultivation– Source of fence posts, fuelwood, and cattle grazing
within the forest.• Shifting cultivation produces complex landscapes
in which old forests, forests at various stages of secondary growth and agriculture co-exist mosaic of patches that are losing or gaining forest carbon stocks
• Should be regarded under REDD+ as leading to degradation not deforestation
Introduction
Introduction• In Mexico shifting cultivation (´milpa´ or ´coamil´) is practiced
by individuals within communal land systems managed by Ejidos. Typically 2 years cultivation/5-10 years fallow. Fallow provides grazing, poles, and firewood.
• Ejidos are the target group of REDD+ policies
• Shifting cultivation systems are highly dynamic which makes it difficult to assess its changes in carbon stocks and the associated causes of those changes.
• Adequate scale , both social and biophysical factors is required.
• Research Objective: – To present analytical framework capable of identifying the
complex of drivers of forest degradation in TDF by using satellite images that provide data at a scale fine enough to detect forest degradation due to shifting cultivation, with on-the-ground survey data on the local use of forest resources.
Introduction
Methods: Study Site
• Ayuquila Watershed, Jalisco, Pacific Coast
• REDD+ Early Action,from Mexican
Government
• Organized Intermunicipial Government
Clearings for Shifting Cultivation
Permanent Agriculture
Regrowth TDF after shifting cultivation
Typical Mosaic Landscape , under different stages of regeneration and clearance.
Research Approach Two components to assess the drivers:
Production of map to assess shifting cultivation at the landscape and community level: The method developed eliminates permanent agriculture from consideration and focuses only on forest cover changes (canopy cover) assoicated with shifting cultivation. For this, SPOT 5 image data (10x10 m) for 2004-2010 were used to map small clearings.
Statistical Model (binary logistic regression) using the map as the dependent variable to assess the factors that can be associated with the probabiligy of forest degradation in shifting cultivation landscapes.
Methods & Materials• Model of the Probability of Forest degradation
Biophysical Variables
Socio Economic Variables
Forest Cover Changes Binary
Variable
Local Surveys Semi structure
Interviews in 29 Ejidos
Remote sensing Data & Ancillary
Spatial Data
•Ratio TDF: •Population•Livestocks•Fence Posts
•Marginalization Index
•Parcel Size
•Elevation •Slope
•Distance to Main Towns
Results & Discussion• Both at landscape and community level clearance and
regrowth are balanced in area, and our measurements suggest that although carbon stocks are on average lower than in ´intact´ TDF, shifting cultivation does not cause net emissions. Regrowth rates are very rapid in first 5 years and soil carbon levels increase.
Forest Cover Change Map (2004-2010) and summary of the landcover transitions
Results & Discussion
Variable Name Estimated coefficient (b ) S.E.
Marginal effect
Slope -0.0545*** 0.0111 -0.5602Dist -0.0326* 0.0163 -0.3352Pop:TDF -0.0157* 0.0066 -0.1614
Fence 0.0003*** 0.00008 0.0031Livestock 0.0002** 0.00006 0.0021HMI 0.7051*** 0.2078 7.2472
MMI 0.48360* 0.2455 4.9706
Parcel_T -0.00037* 0.0002 -0.004
Slope_Elev 0.00003*** 0.00001 0.0003
Constant -1.495*** 0.6880 -17.051
n = 1952, S.E. = standard error of estimation of the model, model log likelihood ratio = -769.39 (df = 10); AUC = 65.1; residual deviance = 1538.7; null deviance = 1605.2. AIC = 1558.78
Binary Logistic Regression Model for the Probability of Forest Degradation associated with Shifting Cultivation
The model predicts changes from TDF to shifting cultivation and vice versa correctly in 65% of the cases
• Flatter areas have a higher probablity of being used for shifting cultivation (For every 1% increase in slope there is 0.75% decrease on the probability of forest degradation). Risk is especially high in flat areas on hill tops.
• Ejidos characterized by lower incomes and less education are more dependent on shifting cultivation, hence highly marginalized communities and medium marginalized communities have a greater probability of forest degradation (7.25 %, 5% respectively) than communities with a low index of marginalization.
Results & Discussion
• Livestock management and use of fencing posts by the ejidos are associated with increases in probability of forest degradation. An increase of 100 posts will mean an increase of 16% in the probability of forest degradation
• Overall biophysical variables (measured at a pixel level) contributed 43.7% of the log-likelihood and community-level information explained around 56.3%.
Results & Discussion
Conclusions and Significance for REDD+
• Shifting cultivation over last 50 years has resulted in lowered carbon stocks in TDF but is not a net emitter of carbon now in the area studied.
• The potential under REDD+ can only therefore be in forest enhancement; strategies which increase the forest stock; possibilities include – Banning shifting cultivation– Increasing length of fallows
Conclusions and Significance for REDD+
• Banning shifting cultivation and e.g. pay PES instead– Socially undesirable (safety net of poorest people)– PES payments based on carbon value would not cover
the opportunity costs– Our other studies show that production of equivalent
quantities of maize in permanent agricultural systems would emit MORE carbon
Conclusions and Significance for REDD+
• Increasing length of fallow– Evidence that fallows have been artificially shortened
in response to government subsidies (PROCAMPO)– Possibility to lengthen fallows limited by land
availability/pop density– Alternative may be to regulate grazing. The impact
of grazing cattle in fallow recovery needs more study.
