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POL469H1 Lecture Notes - Secondary Succession, Cassava, Deforestation

Political Science
Course Code

of 3
IDSB02 Reading- Physical and Human Dimensions of Deforestation in Amazonia
D.L. Skole et al - 1992
Tropical deforestation is important to global climate change, hydrology change and biogeochemical
Brazil has the highest deforestation rates according to some
The understand of tropical deforestation is inadequate b/c:
o Lack of accurate measure of its rate, geographic extent and spatial pattern
o Lack of insight to its causes
Obvious that tropical deforestation is b/c of lots of social, economic & environmental factors but
how they interrelate to effect deforestation vary widely -> some say chiefly pop growth others say
An interdisciplinary approach to analyzing deforestation on Brazilian Amazon needed
Physical Dimensional of deforestation in the Amazon
Landsat and Spot satellite remotes sensors could be used to measure the levels of deforestation
would provide the best info
They could be used to develop detailed maps of rate and extent of deforestation to then document
location and expansion over time
NOAA sensors could be used to locate areas of intense deforestation
The area was mapped from 1978-88 by digitized mappers and satellites which provided an analysis
that was significantly lower than other previous estimates
This data shows that different regions have different levels of deforestation and different time
periods also give different levels of deforestation as well
It is possible to obtain estimates using tabular summaries from government censuses
The data for these areas don’t directly report deforested area but rather on forms of permanent or
temporary agriculture including pastures
Major cause of deforestation in the amazon is agriculture thus the data can be used as a proxy
They census reports also provide info on crop type, farm size, fertilizer use, & other info
When this data was plotted digitally it showed similar geographic patterns to the satellite data
Suggests important role for census data
Region wide patterns of deforestation are the result of many local activities
Net deforestation is the sum of several gross land-cover transitions:
o Primary forest conversion
o Abandonment of agricultural land
o Re-clearing of successional vegetation
These affect biogeochemical cycles and physical processes
The analysis suggests the important and inseparable coupling between active agriculture and
secondary growth
Abandonment rates tend to increase when increases in primary forest clearing produce net increases
in secondary succession area (flood/fire destroyed plant life in secondary succession)
Human dimensions in the Amazon
Satellite observations can provide an objective approach to measure deforestation and it’s possible
to see the geographical patterns into different types of deforestation (mining/farms etc.) but these
alone cannot identify why deforestation occurs or what factor influence regional trends/local
Demographic factors: FOA concluded that population growth was the cause of deforestation globally
One study by Reis and Margulis (1990) states that pop growth relates to deforestation when pop
density is plotted against deforestation density -> multiple regression method related, deforestation
to many anthropogenic causes; density of pop included
However this study does not find that and simple relationships to pop growth may not alone
describe factors driving deforestation in the Amazon
Hecht (1983, 85) concludes that gov’t policy, fiscal incentives and the nature of individual farmers in
an inflationary economy are more significant determinants of deforestation
Other studies confirm this and say that pop growth is one variable in a multiple feedback system
rather than the forcing function
Economic and institutional factors: although deforestation has been occurring for a long time
estimates from satellites show that 90% has happened after 1970 this is thought b/c the events and
conditions happening at a national and international scale has influenced this including:
o Agricultural expansion -> this is the most important agent of deforestation; during the 70s
agriculture expanded esp. in states like Rondonia
o Rondonia had exponential deforestation and during this time new colonization and
settlement programs opened large tracts of forest -> settlement programs and fiscal
incentives to encourage migration from overpopulated, poverty stricken, and drought
ridden areas -> provide opportunities to many landless poor
o Deforestation linked to the economic and demographic changing conditions (seen in state of
Parana as changes in this state directly influenced deforestation in Rondonia)
o Strong external factors created the preconditions for deforestation -> after OPEC increased
the price of oil in 70s lots of money flooded the intl’ money markets; developing countries
like Brazil required foreign capital to fund economic development, industrial programs and
modernization & they needed US $ b/c oil is bought/ traded in dollars
o Brazil’s strategies were to develop its own energy sources in order to reduce the amount of
oil imported and borrow from foreign lenders to develop economic development programs -
> agricultural modernization was one of these
o Brazil’s farmland increased over 60% in the last 20 years and became leading exports of
things like soybeans and oranges & the agricultural modernization programs led to the
change in land tenure and land allocation
o 3 patterns emerged:
1. ½ the total crop area receiving crop credits were used for 3 export crops -> coffee, wheat and
2. largest fraction of crop area was for the production of soybeans
3. little of the land receiving crop credits was for staple foods like black bean and manioc
gov’t programs focussed on replacing coffee with soybeans b/c of highly variable market
soybean yields increased 5x -> combination of land, fertilizers, pesticides, improved seeds, and govt
sponsored credits and incentives produced internationally competitive product
although costs of fertilizers and pesticides high in brazil compared to other countries like the US the
land costs are half that so the overall costs are lower for Brazilian producers
modernization of agriculture also came with structural changes in the economy-> labour intensive
small scale agroindustry to energy and machinery intensive component of the national economy
o land prices rose significantly
o change in land use changed the land tenure -> loss of small scale farms and increase in large
scale commercial and mechanized farms
o increased migration from rural to urban areas
o displaced labourers from mechanization of agriculture & partly higher wages &
opportunities in urban areas
o new migrants cleared land and opened new pastures on Amazonian frontier
o last few years govt programs that have promoted deforestation have been cut back
Interdisciplinary Approach
regional trends are influenced by large scale external forces but mediated by local scale conditions
overall approach would start with direct measurement of the rate, location, spatial pattern and
temporal characteristics of deforestation
satellite remote sensing a tool for making measurements at different temporal and spatial scales
this with combination of sociodemographic data from census documents would provide useful info
on land use, tenure and management
at a second level of analysis case studies and field investigations carried out with satellite data to
gain insight into local scale dynamics of deforestation, abandonment and second growth turnover
causes of deforestation may also relate to external institutional and economic factors satellite data
and field studies cannot conclude everything
ex. Factors that formed the Amazonian Brazil deforestation were the land tenure changes in the
south and changes in the developing economy somewhat catalyzed by the excess petro dollars and
intl’ lending & the change of labour to machinery
migration to Amazon partly response to conditions far removed from Rondonia and not solely b/c of
population growth
deforestation more complicated than too many people
necessary then for a third level of analysis to define large scale external factors influencing