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