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What is Shifting Cultivation? Definition: FAO Forestry Department, “a system in which relatively short periods of continuing cultivation [with a rotation of fields rather than crops] are followed by relatively long periods of fallow” (Lanly 1985). Shifting Cultivation is a form of agriculture, also known as slash-and-burn, or swidden agriculture, in which a plot of forest is cut down, burned, and allowed to dry before being cultivated continuously for several years, after which it is abandoned to revert to natural vegetation. Point out pictures in each stage of shifting cultivation. Burning a plot for shifting cultivation1 A shifting cultivation plot after burning2 Temporary housing in a cropped plot in NE India3
Citation preview
Slash and Burn Agriculture: Incorporating Shifting Cultivation into
a Global Land Use Model for Earth System Model Applications
Claire PlaggeResearch & Discover Internship
Summer 2008
Advisors: Steve Frolking & Louise ChiniAdvisors: Steve Frolking & Louise Chini
What is Shifting Cultivation? Definition: FAO Forestry Department, “a
system in which relatively short periods of continuing cultivation [with a rotation of fields rather than crops] are followed by relatively long periods of fallow” (Lanly 1985).
A shifting cultivation plot after burning2
Temporary housing in a cropped plot in NE India3
Burning a plot for shifting cultivation1
Why is it important to study?
Importance: livelihood for 200-500 million people, its existence impacts soil erosion rates, amount of canopy cover in tropical forests, global carbon cycle (Padoch et al 2007).
Model will be included in the global land use transitions model that provides input to Earth System Models simulating climate change
Shifting cultivation plot in Sambia4
State of Current Research 36 case studies in Central and South America,
central Africa, Southeast Asia, and China from a range of journals
Primarily focused on biological or ecological effects of shifting cultivation, several from a cultural viewpoint
Two large scale studies: Hall et al (1985) and Olofsson & Hickler (2007)
Key Findings Length of cultivation (1-4 years)
Fallow length (3-40 years with average of 5-10) Cleared plot size (0.5-4.0 hectares on average)
Proximity to developed land (very rarely within 100 km)
Population involved (200-500 million), mostly animists/shamanists
Objective Goal: To create a model of shifting cultivation
over time, as part of a larger land use model, based on the shifting cultivation area equation found in Hall et al (1985)
Used Hall equation, adapted to calculate for a gridded global map
Model placed on a 0.5 gridded global map
Shifting cultivation plot in India5
Model for Area of Shifting Cultivation
Asc : area of cultivation + fallow in shifting cultivation
As inputs change with time, the area of shifting cultivation will change with time
€ €
( )2+××××= FPAFRPA needednonpermsc
€
Asc =
( )2+××××= FPAFRPA needednonpermsc
P: population per gridcell in a 0.5° grid
R: the fraction of that population that is rural
P and R were taken from HYDE data (Klein Goldewijk et al. 2008)
€
P × R€
Fnonperm : (constant) the fraction of rural population globally who practices shifting cultivation
Fnonperm was estimated as 0.15 in 1970, 0.11 in 1980/1990, and 0.1 in 2000
Taken from Olofsson & Hickler 2007 estimates of fraction of non-permanent agriculture
( )2+××××= FPAFRPA needednonpermsc
€
P × R × Fnonperm€
Aneeded : (constant) area needed per person for shifting cultivation
Aneeded was estimated at 1/6 hectare based on the average found in the case studies, also the number given by Olofsson & Hickler 2007
( )2+××××= FPAFRPA needednonpermsc
€
P × R × Fnonperm × Aneeded
FP+2: length of fallow period plus 2 years of cultivation
FP was estimated as changing from 8 to 5 years between 1970 and 2000, according to case study averages
( )2+××××= FPAFRPA needednonpermsc
€
FP + 2( )
Shifting Cultivation Area 2000
In km23,000
0
Shifting Cultivation Location Potential vegetation biomass density > 2 kg
C/m2 (this is a rough threshold for forested land) 1 persons/km2 < Population Density < 100
persons/km2
Fraction of urban land per grid cell < 20% Fraction of pasture land per grid cell < 40 % Area of “natural vegetation” land km2 (as given
by HYDE) > 5*Area of cropland km2
World share of GDP per capita < 0.3e-7 Average winter temperature (in February) > -9C Area_sc Crop area
The Modeling ProcessShifting Cultivation Area 2000
In km2
Constraint Mask 2000
Shifting Cultivation Area with Mask 2000
In km2
50
3,000
0
0
Results:The Cultivated Area Map Shifting Cultivation Area (km2) in 2000, with case study
locations
Results: Table of Values
Our model (2000)
Olofsson’s estimates (1990)
Mather’s estimates (1990)
Hall’s estimates (1985)
Highsmith’s estimates (1968)
Total area cultivated
~ 90,000 km2
* * * *
Total population involved
190 million people
583 million people
500 million people
250 million people
200 million people
Total area involved (including fallows)
~ 1,530,000 km2
* ~ 2,400,000 km2
* ~ 36,300,000 km2
Extending the Model Use our model to predict the area of shifting
cultivation back to 1700 or before, as far back as the constraints and variables are available
Use our model to predict the future area of shifting cultivation, and possibly when it ceases to exist
Larger model: included in Global Landuse Model (Hurtt et al 2006), our model will be used as an input to better quantify landuse transitions
The Next Steps Further define Fnonperm, dependent
on constraints, not a constant
Get datasets back to 1700/1500 and predictions up to 2100 to expand the model and find patterns in shifting cultivation land use change
Use socio-cultural variables (such as religion) as a constraint
Shifting cultivator6
Role of Remote Sensing Shifting cultivation plays
role in creation of active fires that are measured by remote sensing
Fields too small for global instruments like MODIS, use local/regional studies with Landsat or Ikonos to observe shifting cultivation plots
Help to understand the measurements gathered by Help to understand the measurements gathered by the proposed NASA satellite DESDynIthe proposed NASA satellite DESDynI
Problems: frequent cloud cover over tropical forests, Problems: frequent cloud cover over tropical forests, highly dynamic landscapehighly dynamic landscape
Fires on Borneo and Sumatra from MODIS7
AcknowledgementsLouise Chini Steve FrolkingStanley GliddenGeorge HurttAmanda Plagge Shifting cultivation plot in
Africa8
Thank you! Are there any questions?
Pictures1. http://exploringafrica.matrix.msu.edu/students/curriculum/m9/activity2.php
2. http://www.natureproducts.net/Agriculture/shifting_cultivation.html
3. http://concise.britannica.com/dday/print?articleId=111207&fullArticle=true&tocId=46122
4. http://www.geolinde.musin.de/afrika/html/t_afr_shifting.htm
5. http://www.megsoil.gov.in/shifting_cul.htm
6. http://www.fao.org/DOCREP/006/AD077E/AD077e04.htm
7. http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17423
8. http://www.geolinde.musin.de/afrika/html/t_afr_shifting.htm