Ch. 10 & 11: Forests & Agriculture Flashcards
(28 cards)
How does the UN FAO (Forest & Agriculture Organization) define a forest?
- Trees covering an area spanning more than 0.5 hectares
-The tree canopy covers more than 10% of the total land area
-Trees grow to a height of more than 5 meters
What is deforestation, forest disturbance, and what is the leading causes of disturbances in Canadian forests?
deforestation - the permanent conversion of forests to other land uses
Forest disturbance - any event or factor that negatively affects the health and structure of a forest
Leading causes of disturbances in Canadian forests:
1. Area impacted by insects (4.5%)
2. Area burned by fire (<1%)
3. Area harvested (<0.5%)
Explain a bit about Canada’s Boreal forest
- More than 186 billion tonnes of carbon are stored there; its the largest terrestrial carbon storage place w/ values doubling those of tropical forests
- The forest is seen as very intact; there’s a low human pop, only a small percent of it has been cleared for agriculture and settlements, however, excluding artic ecozones, 1/4 of the landmass is within 500 m of human access and activity
-also 60% of boreal timber has been logged at least once
What beneficial services do Canada’s forest ecosystems provide?
-The many ecological functions like nutrient and water cycling, carbon sequestration, waste decomposition
-They also offer a place of scenic beauty, where nature-related recreational activities (wildlife viewing, bird-watching, nature walks, etc) can take place
-the financial value of these activities can be important, especially to local rural communities
-Canada is also the 4th largest forest product exporter and leading exporter of softwood lumber and newsprint (largest single contributor to Canada’s balance of trade; bought mainly by the US
Who’s responsible for forests and by how much?
- Provincial gov’t mostly; responsible for about 77% - they manage forest resources on behalf of the public by making agreements w/ private logging companies (such as: forest tenures; give license to harvest in exchange for logging companies fulfilling management duties like reforestation)
- Federal & territorial gov’ts - 1.6% and 13%
- Indigenous ppls - own and manage about 2%
- The remaining 6% is owned by 450,000 private landowners
What is silviculture?
The practice of directing the establishments, composition, growth, and quality of forest stands through diff activities like harvesting, reforestation, and site preparation
What are the common silvicultural systems practiced and what are each of their advantages and disadvantages
Clear-cutting - most commonly applied silvicultural system in Canada; involves removing all trees in a cutblock (designated area of land permitted for timber harvesting) in one operation no matter the species or size. The point is to create a new-aged stand which will be regenerated naturally through replanting
- Advantages: cost-effective, allows easier replanting and tending of the regenerating forest, safest harvesting method w/ the least risk of worker injury
- Disadvantages: nutrients that were stored in the tree bodies are removed from ecosystem, habitats and biodiversity lost, can cause soil erosion in sensitive ecosystems, aesthetically unattractive
Seed tree - method of clear-cutting in which all trees, except for some seed bearing trees, are removed from an area; the seed bearing trees are meant to be the main source of seed for natural regeneration after harvesting
- Advantages: also cost-effective, can result in improved distribution of seedlings and more desirable species mix
- Disadvantages: Regeneration can be delayed if seed production and/or distribution is inadequate
Shelterwood - mature trees are removed by 2 or more partial cuts. The trees leftover are used to supply seed for natural regeneration and shelter for the new advanced regeneration; the leftover mature cover is removed once regeneration is established
- Advantages: Trees after first cut grow faster and increase in value, visually more appealing than clear-cutting
- Disadvantages: complex and expensive to plan & implement, young trees can be damaged during removal of mature trees, and can cause windthrow (uprooting and overthrowing of a tree by wind) which can displace big amounts of soil
Selection - Trees are harvested singly or in groups as they reach maturity. Valuable, mature trees as well as poorly-shaped, unhealthy, and broken, damaged trees are selected to be removed; the point is create and maintain an uneven aged stand
- Advantages: method is favored in areas that value recreation and scenery since harvesting area is less visually unappealing, method results in continuous and regular supply of mature trees overtime; stand quality improves, biodiversity loss is lessened
- Disadvantages: method only successful when applied to shade-tolerant tree species, needs skilled workers to be implemented properly, needs more road and skid trail per unit area, complex and expensive to implement
What is retention silvicultural system?
Retains individual trees or group of trees to :
-maintain structural diversity over the cutblock area for a least one rotation
-leaves more than half of the total area of the cutblock within tree height of the base of a tree or group of trees whether or not the trees are inside the cutblock
What is biocide used for?
-It’s used on forest lands to reduce competition for seedlings on replanting sites
- also to protect seedlings from insect damage
-Chemical are used to suppress early successional species and compress their successional time span in order to maximize the growth potential of more desirable species (usually conifers)
Explain fire suppression
It’s important to protect lives, property and commercially available timber, but fire is also very important to the natural cycle of forest ecosystems; it initiates secondary succession as it renews vegetation
-fire suppression results in ecological changes not characteristic of fire-dominated ecosystems
-in the absence of recurring fires, ground fuel could accumulate, increasing risk of major wildfire event
Compare and contrast fire-dependent, fire-independent, fire-initiated, and fire-maintained systems
Fire-independent - plant species develop no new fire adaptations; the effects of fire on them are dramatic and long-lasting, and post-fire recovery is real slow (ex/ floodplain forests, wetlands, alpine ecosystems)
Fire-dependent - Fire is common and the plant species are adapted to fire and need it for their existence; post-fire recovery is immediate and fire exclusion is unnatural (ex/ grasslands, lodgepole pine)
Fire-initiated - fire plays an important role in initiating long-living plants; the initial revegetation is fast, however, the post-fire recovery takes a really long time, possibly hundreds of yrs (common in temperate regions like Western larch, coastal Douglas-fir)
Fire-maintained - light-intensity fires are common while crown fires aren’t; individual plants tend to survive these fires which thins the stand and decrease fuel loads and select against fire-susceptible species; all this keeps maintaining the community at an early or mid-successional stage (ex/ interior Douglas-Fir, Ponderosa Pine)
What are some characteristics of old-growth forests and what distinguishes them from younger stands?
Characteristics include:
-supply high value timber
-contain large amounts of carbon
-contain large reservoir of genetic diversity
-Provide habitat for many species
-Regulate hydrologic regimes
-Protect soils and conserve nutrients
Distinguishing old-growth from younger stands:
- larger trees for species and site
-There’s a wider variation in tree sizing and spacing
-Accumulations of large dead, fallen, and standing trees
-Multiple canopy layers
-Canopy gaps and understorey patchiness
-Dead and decaying biomass in form of broken tops or boles and root decay
What is the Great Bear Rainforest Agreement?
It was/is a collaborative effort from Indigenous ppl, gov’t, environmental groups, and the forest industry that offered significant increase in protected areas and greater recognition of indigenous concern
-Process took over 20 yrs, but 2016 it was signed
-Takes a ecosystem-based approach
How can forest harvesting contribute to soil erosion? What are the key factors that also contribute? How can we reduce soil erosion?
-On steep slopes in areas w/ heavy levels of precipitation
-loss of site fertility
-Flooding and destruction of fish habitat
Key factors contributing are usually poor road design and maintenance
we can reduce forest soil erosion by these strategies:
-Leaving buffer strips along watercourses
-Minimizing soil disturbance
-developing good road building practices
How can forest harvesting impact hydrology?
Large amount of trees have a role that removes a lot of water in the atmosphere through transpiration, so removal of a bunch of trees reduces the transpiration process and other storage capacities, usually leading to flooding
How can forestry affect climate change?
Because of forests’ abilities to absorb and release large amounts of carbon in the atmosphere, it plays a big role in the global carbon cycle
-big changes in forest carbon sinks and sources can affect climate by changing the amount of carbon in atmosphere; massive deforestation can increase it, making emission in air worse for climate change
What are the UN global forest goals?
- Reverse loss of forest cover worldwide
- Enhance economic, social, and environmental benefits
- Increase area of protected and sustainably managed forests
- Strengthen scientific and technical cooperation
- Promote governance frameworks to implement sustainable forest management
- Enhance cooperation, coordination, coherence, and synergies across sectors and stakeholders
What are the 3 kinds of agricultural land?
- Arable land - occupied by crops that need yearly re-planting (or fallow land or pasture; they need 5-yr period re-planting)
- Permanent cropland - Where crops (like coffee, tea, fruit) don’t need annual re-planting
- Permanent pastures - used mainly for grazing livestock
What is one of the arguments for a vegetarian diet in terms of the food chain?
That by eating at the lowest level of the food chain (as herbivores), humans will maximize amount of usable energy in food system
Explains the stats of meat consumption: who’s eating more meat and what does it imply for the future?
- Canada still has highest meat consumption (91 kg per yr); consume significantly more than global avg(43 kg per yr), but it’s decreased slightly now than how it used to be
-European Union meat consumption is 70% higher than WHO recommendations
-Meat consumption is widely diff by region and socioeconomic status
-If global diet trends continue, the demand for global livestock feed will double by 2050
How is agriculture contributing to climate change?
- Ever since agriculture started, w/ the domestication of plants and animals, the deforestation and conversion of complex natural systems to simple control systems, it caused a big bump in atmospheric CO2 levels 8000 yrs ago
-1 billion tonnes of soil organic carbon has been lost in Canada ever since we started crop cultivation
-about 30% of carbon in organic soil layers has been lost
-but some agricultural productive areas are now acting as carbon sinks due to improved farming techniques which started recovering carbon-depleted soils
-Nitrogen being transported off-farm (from soil organic matter from decomposers) through leaching, runoff, and evaporation
-There’s also a lot of Nitrous oxide (N2O) emissions from increased use of fertilizers
-Livestock are significant source of methane (NH4), and N2O emissions
What are the potential impacts of climate change on crops and livestock in diff regions/continents of the world?
North America:
-Production of major crops might decline relatively slowly by mid-century, but more steeply by 2100
-Climate will favour fruit production in Great Lakes region while late-season heat stress will challenge US soybean production
-reduced precipitation will restrict water availability as irrigation demand increases
Latin America & Caribbean:
- in temperate areas, soybean, wheat, and pasture productivity increases
-drier soils and heat stress reduce productivity in subtropical and tropical regions
- salinization and desertification increased in arid zones like Chile and Brazil
-Rain-fed agriculture in semi-arid zones face higher crop losses
Europe:
- Temperate and polar regions benefit from change
-initial benefits in mid-latitudes turn negative w/ higher temps
-high temp increase livestock mortality risk
-climate-induced diff in wheat production increase in southern and central europe
Sub-Saharan Africa:
-Overall impacts on production of cereals, especially maize(corn) will be negative across region
-frequency of extremely dry and wet yrs increase (most of southern Africa is drier; rainfall will increase in East & West Africa)
-Rangeland degradation and drought in Sahel reduce productivity
Near east and north Africa:
- rising temps threaten wheat and maize production
-general decline in water availability; slightly more in Sudan and southern Egypt
-Warm winters benefit livestock but summer heat stress have negative impacts
Asia:
- Agricultural zone will shift northward as freshwater availability declines in south, east, and southern Asia
-Heat stress limits livestock expansion numbers
-higher temps during critical growth stages cause a decline in rice yields over large portion of the continent
Oceania:
- In New Zealand, wheat yields rise slightly but animal production declines by 2030s
-In Australia, soil degradation, water scarcity, and weeds reduce pasture productivity
-High temps increase water needs of sugercane
What can be done in agriculture to reduce global warming?
-Reducing number of livestock by eating less meat
-No tillage cultivation , reducing summer fallow
-Planting perennial crops, maintaining nutrients
-Ways of reducing nitrogen fertilizer input
Explain the green revolution
It refers to the technological advancements made to increase productivity of agricultural lands. This includes creations like:
-Chemical pesticides
-auxiliary energy flows in form of fertilizers
-Higher-yield seeds (shorter maturation, drought resistance)
-genetic engineering
-complex irrigation systems
-Modern farming equipment (tractors for seed sowing and plowed, mechanized food processing
High producing seeds lead to significant increase in grain supply throughout the world (miracle rice, miracle wheat); this relied on genetic combination found in nature (through cross-breeding different varieties of the same species)
-directly contrasted with GMOs, which involves combining genes from 2 different unrelated species
-The green revolution really helped with food supply; if developments weren’t created, world would be suffering from chronic food shortage
-but this revolution also has negative impacts that will ultimately lead to long-term productivity loss. this includes:
-improved varieties only produce well w/ fertilizer and pesticides (leading to even greater dependence on fertilizer)
-Poor framers can’t afford these inputs
-narrower genetic base
-Monocultures lead to pests and disease vulnerability
