Lecture 28-33 Flashcards
Land use change def
Conversion of existing natural ecosystems to other forms of landscape (generally for anthropogenic use)
What are land use changes associated with agriculture?
deforestation (lost roughly 25% of global land area) –> europe is incredibly deforested
draining or modifications to wetlands
modification of grasslands
How does deforestation impact the carbon cycle?
It impacts atmospheric CO2: 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 (so does carbon sequestration)
therefore, uptake of atmospheric carbon is reduced due to deforestation
- annual plants (crops) do not sequester as much carbon as trees –> lesser permeance than trees
- animal (pasture land) emit GHG through respiration
Carbon stored in wood is ultimately returned to the atmosphere through decomposition
How does deforestation impact the hydrological cycle?
Trees are a major part of the recycling of green water, even more so than other plant groups
A large tree pop. can actually impact local weather patterns through a high degree of transpiration and cloud-seeding secondary chemicals
Influence cloud cover
Explain the flying river
Density of plant life in the Amazon rainforest impacts weather patterns
Aerial river: system which brings moisture over large areas as a result of wind currents and significant plant transpiration. Water evaporated from the tropical atlantic ocean is brought by winds–produces rain but the air is recharged by recycled forest moisture. After reaching the mountains, moisture condenses and produces precipitation along the Andes. The rest of the moisture produces rainfall in Southeastern South America.
Enough trees must exist to keep the river flowing. Failure of the flying river will likely cause the reduction in rainfall in many places –> tipping point to greater forest loss in the Amazon.
What are the impacts of deforestation on nutrient cycles?
High rates of precipitation in tropical forests: soil nutrients released through burning quickly lost in soil
Area burned becomes unproductive quickly: needs burning of new virgin forest for continued harvest
Slash-and-burn agriculture
Farming technique involving the removal of woodland through the use of fire, and the farming of that land using the nutrient-rich ash as fertilizer
most common in areas with poor soil fertility (tropical areas), low GDP, and high rates of poverty (primary method for deforestation in the Amazon)
What are the impacts of deforestation on radiation budget?
Canopy cover is dark in colour –> has low albedo
Cropland and pasture actually better for albedo than tree cover –> reflect more solar radiation
What are the impacts of deforestation on biodiversity?
Forests harbor the highest levels of biodiversity for terrestrial species
Land use change leading to habitat loss of degradation –> most significant cause of species extinction risk
Land use change and biodiversity are not equally distributed globally
What is the impact of agriculture on grassland?
temperature grasslands are the most endangered biome on most continents
grasslands biome seized for cropland and pasture
- much less effort required to convert to agriculture than forest or wetlands
pasture is not equivalent to native grasslands
- completely different species assemblages
- many more native species in grasslands
- biodiversity loss
What is the role of grasslands in the carbon cycle?
grasslands may be a more reliable form of carbon sequestration than forests under a regime of increased forest fire frequency under climate change
grasslands store more carbon in soils than in aboveground biomass (roots and soils survive forest fires)
What are the impacts of agriculture on wetlands?
50% of global wetlands have been drained for agriculture 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 consequences of wetland loss?
1) Conversation 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
2) Change in GHG cycles:
- Artificual fertilizer increasing production of nitrous oxide
- Changes in production of methane of CO2
3) Soil degradation
- Loss of soil organic matter
4) Loss in biodiversity
- Most wetland species are olbigate to that type of ecosystem (cannot live outside of a wetland)
5) Ecosystem services such as water filtration and flood prevention
What is urban expansion?
Agriculture is usually situated near human habitation
As cities grow, expand outwards and growth eventually overtakes. Agricultural land is converted to urban space
How does urban expansion impact environmental systems?
Changes local radiation budget
Changes local hydrological cycles
Changes carbon cycle
Changes nutrient cycle
Biodiversity loss
How does urban expansion change radiation budget?
most man-made surfaces have a low albedo
urban heat island: increased temperature resulting from heat radiating from low albedo man-made structures
How does urban expansion change the hydrological cycle?
Covering land surfaces with non-porous coatings (asphalt) contributes to uncaptured runoff and slows/prevents groundwater infiltration
Surface mining consequences
dramatically alters landscapes: removal of forest, wetlands or grasslands
alter morpology of the landscape
Mountaintop removal mining consequences
removal of all biomass and mass modification of the geology of a region
permanently alters the topography of a landscape –> changes how water and sediments move through the environment
Impacts of surface and sub-surface mining
Chemical contamination of the lanscapes
Some mined substances need processing before market or require chemicals for extraction
- Chemicals used in these processes often highly toxic
- Long history of improper storage of these chemicals in the mining industry
Reforestation
Potential to remove 25% existing atmospheric carbon
Effort goals:
- reduce soil erosion and occurrence of sandstorms
- significant contributor to meeting GHG reduction goals
- recreate a local timber industry
- support local biodiversity (many species dependent on tree cover for survival)
- cultural pride
Reforestation in Iceland
Rapid and extensive desertification (land degradation in arid, semi-arid, and dry sub-humid areas) resulted in Iceland
- Land degradation where biological productivity of soil is lost
High winds
- stripped soil and produced deadly sandstorms
What are some challenges with reforestation?
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
Replanting trees does not replicate natural species’ richness
- Does not replace dependent species
- Some will return, but some do not naturally reoccur after deforestation
Ecosystem services
Outputs, conditions, processes of natural systems that either directly or indirectly benefit humans
- Benefits can be essential or simply helpful
- Benefits can be material or social
Involved aspects of hydrology, biogeochemistry, ecology, and economics
Briefly recount the timeline of the ecosystem theory
Pre 1970s: we are self-sufficient as a species (domination of nature, can solve any shortcoming through technology)
1970s: ecosystem service concept popularized as a conservation framework –> protect the environment movement
1990s: ecosystems provide a service that can be quantified and valued monetarily
2003: Millennium ecosystem assessment project funded by UN
What is the Millennium Ecosystem Assessment?
Ecosystem services can be categorized into 4 main types:
1) provisioning services
2) regulating services
3) cultural services
4) supporting services
Provisioning services
goods/products derived from ecosystems
examples:
- food resources (plants, animals, fish)
- freshwater
- raw materials (wood, fibers, oils)
- energy (biofuels)
- pharmaceutical resources (traditional medicines and sources of new pharmaceuticals)
Regulating services
The benefits obtained from the regulation of moderation of natural processes
Examples:
- moderation of extreme events
- air and water purification
- climate regulation
- carbon storage
- decomposition
- prevention of soil erosion
- pollination
What is an example of moderation of extreme events (regulating services)?
Mangroves reduce damage from floods, hurricans, droughts.
They protect shorelines from exreme wave events, and also provide additional ecosystem services, for example in the form of products (fish)
How is air purification a regulating service?
Plants purify air through several different mechanisms
- CO2 removal through photosynthesis
- Removal of particulate matter that is dangerous for humans (plant leaves are covered in wax or hairs that particulate matter sticks to. When it rains, it bring the particulate matter to the soil where is it less likely to go back into the atmosphere)
- Nitrogen fixation in leaves –> mediated by symbiotic bacteria
How is water purification a regulating service?
Waste-water treatment: specific components of aquatic communities are excellent at removing and purifying elements of water contamination
Wetland plants naturally remove excess nitrogen and phosphorus from agricultural fertilizer runoff
Uptake contain heavy metals from soils (can then be removed, taking the heavy metals with them)
Mussels (and other bivalves):
- filter feeders
- will concentrate pollutants as they consume phytoplankton (microplastics, pesticides)
What are constructed wetlands?
Artificial wetlands designed to maximize the water filtration potential of a wetland ecosystem
How is erosion prevention a regulating service?
erosion prevention and maintenance of soil fertility: soil erosion is a key factor in the process of land degradation and desertification
What role do decomposers have in regulating services?
Major role in the carbon cycle and supporting heterotrophs and photosynthesizes
- complex organic molecules reduced to atmopsheric CO2 or different simpler carbon molecules
Release of minerals and elements into the environment for further use by life
Role in suppressing disease transmision in communities (example vultures only eat dead matter –> important scavenger and effective rapid decomposers)
How is pollination a regulating service?
Estimated 35% of crops directly dependent on pollination for production of harvestable product
- 33% of all plant species require a pollinator for seed production
- loss of pollinators would see seed production reduced by 80% in half of all flowering plant species
Cultural services
include non-material benefits that people obtain from ecosystems such as spiritual enrichment, intellectual development, recreation and aesthetic values
Example:
- River in New Zealand given legal personhood under law
- India gave the Ganges and Yamuna River status as lining humans under the law
Supporting services
ecosystem services internal to ecosystems, maintaining ecosystem integrity, funcitoning, and resilience and the capacity of ecosystems to produce provisioning, regulatory and cultural services
examples:
- photosynthesis
- nutrient cycling
- water cycle
- soil formation
- genetic resources
- habitat
Allelic diversity
the variety of alleles between and within populations of species
provides genetic resources for
- improving commercial crops and livestock
- adaptation to environmental stressors (wild and domestic species)
How are genetic resources a supporting service?
Species are not uniformly genetically identical across their range
Local adaptation fueled by environment and local genetic mutation
- Create substantial allelic diversity across the range of a species
Genetic adaptations within an isolated sub-population may be useful for adapting to climate change
Example: genetic engineering program that produced american chestnut trees which are highly resistant to fungal disease
Genetic resources with the chestnut tree
Single-gene insertion (a wheat gene)
Produces a single enzyme
Destroys a compound in the pathogen called oxalate
- pathogen uses oxalate to initiate the infection
Without oxalate, pathogen cannot infect a chestnut
- Effectively making the trees immune
Release of teh transformed American chestnut would be a major paradigm shift for conservation
- The first genetically modified organism which has been created to replace a non-transformed native species
Economic valuation of ecosystem services
major application of the ecosystem services concept in the 21st century
- assigning an economic valuation in order to value the loss of these services
How much is someone willing to pay to have a service or to pay to not be without a service (WTP and WTA)
Valuation likely to differ at the local scale
Benefits of ecosystem services may not be direct (externalities)
Externalities definition
cost of benefit received by a third party who had no control over how the cost of benefit was created
The Economics of Ecosystems and Biodiversity (TEEB)
Study attempting to quantify economic valuation of global biodiversity
Amazon Fund
21$ billion fund support alternative economic development in Brazil, halt deforestation
Norway –> 1$ US billion
Germany, USA, UK –> pledged 5$ US billion by 2020
What are the primary drivers of biodiversity loss
habitat loss
invasive species
overexploitation
pollution
climate change associated with global warming
influencers: humans pop. growth, increasing consumption, reduced resource efficiency
Contaminant def
presence of, or elevated concentrations of, a potentially toxic substance in the environment
Pollution def
contamination that results in measurable effects on natural processes (abiotic or biotic)
Primary pollutant def
pollution that is produced directly from a source
Secondary pollution def
primary pollutants undergoing chemical changes within a natural reservoir, forming a different form of pollutant
Bioaccumulation def
toxin levels increasing in the body tissues of an individual during its lifetime
limited to the lifetime of an individual
biomagnification def
toxin levels concentrating in higher trophic levels
species of higher trophic levels –> higher concentrations of these pollutants
What are some natural sources of pollution?
Volcanoes releasing large qties of gaseous pollutants
Fossil fuels leaking into natural bodies of water (petroleum seep)
What are the 4 main groupings of pollution?
Land pollution
Air pollution
Water pollution
Energy pollution
Land pollution
Deterioration of land surfaces (above or below ground) as a result of contamination
Common examples:
- Landfill
- Soil contamination
- Pesticides and herbicides
Often the source of contaminants which enters water or air reservoirs
Litter/landfill
disposal area for solid waste
landraising: piling solid waste on the surface
landfilling: digging a hole for the burying of solid waste
What are modern landfills?
Multiple layers of protection to contain solid waste and leachates within the landfill
Sealed with impermeable layer –> low impact on environment
- risk of seal breaking and leaking
Designed to be buried once filled and converted to greenspace
These produce methane (because sealing it prevents access to oxygen)
Soil contamination
Any substance present in a soil which is potentially harmful to human health
- both manmade substances and exceedingly high levels of natural substances
examples:
- heavy metals
- pesticides and herbicides
What is the risk with urban horticulture?
Urban soils are often heavily contaminated after successive generations of urbanization
Plants take up heavy metals in soils and incorporate into tissues
Urban horticulture may be exposing populations to heavy metals from contaminated metals
Pesticides DDT
DDT was the first known pesticide that could effectively kill a wide number of different insect species
Widely heralded as a miracle compound (relatively non-toxic to humans)
Applied very liberally
DTT can both bioaccumulate and biomagnify
- entered food chains through water and soil contamination
Banned 1970-1980s
DDT in birds
High levels of DDT interfered with calcium metabolism
Female birds contamined with high levels of DDT produced eggs with eggshells too thin to incubate
- The female would crush the egg shell during incubation
Resulted in significant declines in several bird species
Water pollution
pollution of blue water resources
Example:
- human sewage
- PCBs
- Mercury
- heavy metals
- fertilizers
- oil spills
- pharmaceuticals
Mercury
Cycles through atmosphere, water and soils
Natural sources –> volcanoes, fires, chemical weathering
Anthropogenic activities –> coal burning, mining, waste incineration
Mercury causes the greatest rates of harm once it enters water systems
