Lecture 28 Flashcards
Ways that humans take resources from their environment
Biosphere (hunting, gathering, logging, agriculture), hydrosphere (water, fishing, salt), geosphere (minerals, fuels, building materials), atmosphere (oxygen)
Waste products are returned by humans when taking resources from the earth
to lithosphere (solid waste), to hydrosphere (dissolved material), and atmosphere (gases and aerosols)
Renewable resources
those replenished by growth each season
examples of renewable resources
crops, wood, running water, fisheries
Non-renewable resources
those replenished only on longer timescales
examples of non-renewable resources
minerals and fossil fuels
Open system (old resource management)
Resource use was viewed as a process of extraction from the environment from seemingly limitless resources, used by humans, and disposal wastes and by-products back into the environment.
Human population and resources
Technological advances have allowed for dramatic increases in the human population, putting increased strain on Earth’s resources and environment
Closed-system earth
Earth itself is a closed system, so wastes and by-products (pollution) returned from extraction, production, manufacturing, and consumption directly impact the human economy. Earth’s resources are not unlimited and that conservation, efficiencies in extraction, manufacturing, and transportation of goods, and recycling / reuse are needed leads us to the modern resource cycle
We can extend resources through:
conservation, reuse, recycling, or substitution.
Stock is depleted if the resource is withdrawn at a rate ___ than the rate of replenishment.
faster
Responsible resource management
use resources at a rate that does not exceed the replenishment rate
If a renewable resource is severely depleted, it will not be able to _____.
regenerate
Forest harvesting techniques:
clear-cutting (non-sustainable), cut blocks, and selective harvesting
Clear-cutting forest harvesting
This resulted in the loss of root systems that hold soils together causing widespread soil erosion, nutrient loss, and accumulation of debris in rivers and streams.
Cut-block forest harvesting
small clear-cut areas surrounded by forest are harvested.
Selective harvesting
(thinning) where only trees of a certain maturity are removed to a level that prevents ecosystem damage.
Deforestation negative effects
- forests are a carbon sink, and deforestation leads to losses in carbon sequestration from the atmosphere
- loss of habitat biodiversity, habitat, and soil worldwide
- tropical forests are susceptible to deforestation because tropical soils are nutrient-poor, and experience greater erosion with shallower root systems
Fisheries
useful for: animal protein consumption, oils, or fishmeal for animal consumption.
Methods of fisheries harvesting
capture fisheries and aquaculture
Capture fisheries harvesting
those in which fish are caught in the wild, and this contributes nearly 100 million metric tons/year
Aquaculture
the raising of fishery resources in captivity – is used primarily to raise high-value products (shrimp, salmon), and contributes an additional 50 million metric tons/year.
Cons of capture fisheries
can lead to overexploitation
Cons of aquaculture
may cause the loss of natural coastal environments, requires considerable resources to run, and can lead to the spread of disease in the fish population
Continued overuse of fishery resources can lead to _______
commercial extinction – so few organisms remain that it is not economically feasible to continue to harvest them
Estimates are that ___ of global fisheries are overexploited, with another __ fully exploited
50%
25%
Soil Resources
Arable soil is essential to the global food supply (human supply and production of feedstock and cattle). Soil supplies essential nutrients for plant growth and takes hundreds to thousands of years to develop.
The soil profile is comprised of ___, starting with: and ending with:
horizons
weathered parent rock and ending in organic oxygen-rich O-horizon at the surface
Soil horizons:
O (organic matter), A (mixed mineral and organic matter), E (removal of soluble material), B (accumulation of clay), C (weathered parent rock)
Threats to soil resources
loss of nutrients due to overproduction, contamination from agricultural practices, herbicides, industrial activities, over-fertilization, and compaction.
Soils form on timescales that are _____ of years, while global soil loss is occurring at __ per decade
thousands years versus 7% per decade
How to minimize soil erosion
employing proper crop rotation techniques (including allowing fields to be fallow periodically), preventing soil pollution, terracing on sloped land, and optimizing irrigation, pesticide, herbicide and fertilizer applications
Over-fertilization causing Eutrophication
When excess nutrients – especially phosphorous and nitrogen – leach from agricultural fields to freshwater bodies, algae, plankton, and aquatic weeds grow. As these organisms die, the process consumes oxygen in the water, causing the water to go anoxic. This, in turn, kills other organisms living in the water
Water resources are needed in:
food production (animal and plant), energy generation, transportation, recreation, and industrial processes
Irrigation is by far the largest consumer of water globally, comprising more than __ of use, with industrial uses comprising an additional __.
75% and 20%
How water can be lost:
industrial contamination, the overuse of groundwater aquifers (causing their compaction), and increased evaporation due to climate change or deforestation
Costs of damns
habitat loss, the modification of river ecosystems, modifications to seasonal discharge rates and patterns, and a reduction in sediment transport downstream (which can cause deltas to retreat).
Arak Sea in Kazakhstan
a classic example of overuse. Beginning in the 1960’s, water was diverted from rivers that feed the sea for irrigation projects. A once thriving fishing industry collapsed, and all that remains of the ‘sea’ is a thin strip of saline water.
Ogallala aquifer in the central part of the United States
water levels have dropped by well over 90 meters and the land surface has dropped 10’s of meters due to agricultural and industrial consumption exceeding the rate of recharge.
