Lec 27: Land Transformation Flashcards
what is Land Use Change
the conversion of existing natural ecosystems to other forms of landscape (generally for anthropocentric use)
rn: 12% of ice free land is for crops
24% is for pasture
what are the 3 common changes to natural systems for agriculture
- deforestation
- draining or modification to wetlands
- modification of grasslands
how much forest did we originally have?
55% of global land area
how much forest did we lose?
roughly 25% of global land area
Deforestation and the carbon cycle
atmospheric CO2: the trees are a major source of carbon sequestration
carbon is required to build the persistent woody structure of trees
trees do not sequester carbon at the same rate throughout their lifecycle
growth slows as the trees reach maximum height and so does carbon sequestration
outcomes of deforestation on carbon sequestration:
uptake of atmospheric carbon reduced
annual plants (crops) do not sequester as much carbon as trees (lesser permeance than trees)
animals (pasture land) emit GHG through respiration
carbon stored in woods is ultimately returned to the atmosphere through decomposition
deforestation and the hydrological cycle
- trees are a major part of the recycling of green water (even more so than other plant groups)
- a large tree population can impact local weather patterns
- influence cloud cover
How do large tree populations impact local weather patterns? (density of plant life)
- high degree of transpiration
- cloud-seeding secondary chemicals
What are flying rivers?
aerial river , a system which brings moisture over large areas as a result of wind currents and significant plant transpiration
what is needed for a flying river to function? and what does it entail?
enough trees must exist to keep the river flowing
this means that if 20-25% of the amazon is removed it will reach a tipping point which will stop the function of the amazon flying river
we are currently at a 17% loss
what are the implications of the loss of the amazon flying river due to deforestation?
- reduction in rainfall in southern brazil, as well as Argentina, Paraguay, Uruguay
- loss of rainfall likely a tipping point to greater forest loss in the amazon
How is deforestation linked to nutrient cycles
through the slash-and-burn agriculture technique
what is slash and burn agriculture
a farming technique involving the removal of woodland through the use of fire, an the farming of that land using the nutrient-rich ash as fertilizer
where is the SAB technique most used?
most common in areas with poor soil fertility (tropical areas), low GDO and high rates of poverty
it is the primary method for deforestation in the amazon
how does the SAB technique impact the nutrient cycles
- high rates of precipitation in tropical forests = soil nutrients released through burning are quickly lost in soil
- the area burned becomes unproductive very quickly -> necessitates burning of new virgin forest for continued harvest
What links deforestation and the radiation budget
- albedo (canopy cover is dark in color, has a low albedo)
- cropland and pasture actually better for albedo than tree cover (reflect more solar radiation)
deforestation and biodiversity
- forests harbour the highest levels of biodiversity for terrestrial species
- land use change leading to habitat loss or degradation (most significant cause of species extinction risk)
- land use change and biodiversity are not equally distributed globally
what is the most endangered biome on most continents
temperate grasslands
why are temperate grasslands endangered?
- 75% of native grasslands in Canada have been lost
- Only 1% is protected in Canada, 4.5% globally
- Grasslands biome seized for cropland and pasture (much less effort required to convert to agriculture than forests or wetlands)
- pasture is not equivalent to native grasslands (completely different species assemblages, many more native species in grasslands, biodiversity loss)
What links grasslands and the carbon cycle
grasslands may be a more reliable form of carbon sequestration than forests under a regime of increased fire frequency under climate change
grasslands store more carbon in soils than in aboveground biomass (roots and soils survive forest fires)
T or F: grasslands are better carbon sinks than forests
true
what is the impact of agricultutre on wetlands
50% of global wetlands have been drained for agricultural production
existing wetlands can be modified for rice production (dramatic loss of biodiversity in modern rice cultivation)
modification of existing water systems for irrigation (change in sedimentation rates can result in loss of landmass)
what are the impacts of the loss of wetlands
- conversions of a green and blue water reservoir to a system which holds much less water, for a shorter period of time (loss of water to runoff, or rapid turnover through transpiration)
- Change in GHG cycles:
- artificial fertilizer increasing production nitrous oxide
- changes in production of methane and CO2 - soil degradation (loss of soil organic matter)
- loss of biodiversity
- most wetlands species are obligate to that type of ecosystem (cannot live outside of wetlands) - ecosystem services such as water filtration and flood prevention
in what ways do urban environments impact environmental systems
- local radiation budget (urban heat island)
- local hydrological cycles (non-porous coatings)
- carbon cycles
- nutrient cycles
- biodiversity loss
what is Urban Heat Island
increased temperature resulting from heat radiating from low albedo man-made structures
what is an example of localized cooling
Almeria, spain: largest and densest concentration of greenhouses in the world, the high albedo of white greenhouses results in a localized cooling (-0.9 C)
what is the impact of covering land surfaces?
it contributes to uncaptured runoff, slows and prevents groundwater filtration
T or F: Mining has a bigger impact globally than agriculture
FALSE
what is a surface mining
removal of forests, wetlands or grasslands ,
can dramatically alter morphology of the landscape
What is mountaintop removal
removal of all biomass and mass modification of the geology of a region
permanently alters the topography of a landscape
what is the impact of surface and sub-surface mining
chemical contamination of landscapes
what is the danger regarding the extraction of chemicals
chemicals used in these processes are often highly toxic,
with a long history of improper storage of these chemicals in the mining industry
case study of deforestation in iceland (desertification)
they went from 30-40% of forest land to 1.5-2% after human settlement
resulted in land degradation where biological productivity of soil is lost
this desertification in addition to high winds produced deadly sandstorms
goal of reforestation up to 5% by 2050
what are the effort goals of reforestation
- reduce soil erosion and occurence of sandstorms
- meeting GHG reduction goals
- recreate a local timber industry
- support local biodiversity
- cultural pride
what are the hurdles of reforestation efforts
- the remaining soil is of very poor quality (little organic matter)
- lack of other plants to help support tree growth (herbaceous species improve local moisture through transpiration + support microbial communities essential for healthy plant growth)
- short growing season (carbon sequestration is related to growth rate, short season = slow growth)
- feral sheep are common (most trees planted are seedlings, easy food for sheep)
what is a limit of reforestation
replanting trees does not replicate natural species richness
do not replace dependent species (some will return but some do not naturally reoccur after deforestation)
