Transcript Watershed Structure and Function Related to Ecological

What environmental issues arise
related to these human activities?
Three Subdisciplines of Environmental Science
1.
Population
a. size of population
b. impact per person
2. Resources
a. non-renewable - finite supply
b. renewable if "husbanded suitably"
exploitation=mining, therefore nonrenewable
e.g. soil fertility in agriculture and forestry
3. Environment
Anthropogenic or natural influences affect abiotic or biotic components of biosphere
Pollution affects ecological health, human health and quality of life
Ecosystem (Individuals, Populations, Communities, Ecosystems,
Biome, Biosphere)
Biodiversity: Genetic, Species, Landscape
Growth of Human Population
Discussed here because it drives human impacts on environment
Humans are most numerous large mammal
Cultural progress increases population density
5 million individuals before agriculture (10,000 years ago)
300 million and 500 million at 0 and 1650 AD, respectively
then improved medical treatment and sanitation
reduced death rates
technology advances in resource extraction,
manufacturing and agric.
discovery by Europeans of unused lands
with rich natural resources
Growth of Human Population
1 billion by 1850
2 billion by 1930
4 billion by 1975
5 billion by 1987
1500
1750
2000
6 billion on Oct. 12, 1999
Growth decreasing from 2.6% in 1960s to 1.7% per year
(98 million people/yr)
reach stabilized population density about year 2100
>10 billion
Population Growth - Put into Perspective
6 Billion People
Bison maybe > 60 million
probably highest number of large mammals other than man
Human Symbionts
4 Billion Domesticated, Large-Mammal Symbionts
sheet, goats, cows, pigs, & fewer horses, camels, water buffalo
Small Animals........12 billion chickens
Plants - Crops
Compare to:
15-30 million crabeater seals in Antartic
40-60 million white-tail deer (that we helped)
Effects of Human Population Growth
•Humans & their symbionts (animal & plant)
cause great shift in biological balance of the
biosphere
•Biological as well as Chemical and Physical
•Most anthropogenic impacts on the biosphere
can be thought of as stresses
•Stress="environmental influence that causes
measurable ecological changes, or that limit
ecological development"
Natural Stressors
Natural Stressors - important as stressors and
as case studies of ecosystem response to stress
Physical stress - tornados, hurricanes, tidal waves, earthquakes,
and glaciers (longer time scale)
Wildfire
Climatic or Weather Stress - temperature and moisture stress,
usually high temps and low moisture
Biological Stressors
Competition, herbivory, predation, parasitism, and disease
Human Stressors
Rapid mining of non-renewable resources
Overharvesting (exploitation) of renewable resources
Forestry and agriculture mine soil fertility
Chemical pollution: fertilizers, pesticides, toxic elements
Thermal (power plants and global climate change)
Radiation stress (nuclear wastes and ionizing radiation
also increasing with ozone depletion)
Habitat Alteration, Fragmentation, and Depletion
Ecosystem Responses to Stress
Different for short-term and long-term changes in environmental
conditions
Short-term change = pulse disturbance
decrease in biomass of organisms & change in sp. comp.
related to resistance of organisms to the disturbance
recovery in biomass of organisms related to:
resilience of organisms
growth rates of organisms in habitats with specific fertility
typically have recovery of community that has similar species
composition and biomass of community before disturbance
if have no lasting change in habitat (e.g. toxic contaminants)
Pulse Disturbance
0%
Low
Species Relative Abundances
High
Biomass
100%
Disturbance
Time
Ecosystem Responses to Stress
Long-term change=press disturbance
maybe decrease in biomass of organisms &
surely a change in species composition
related to resistance of organisms to the disturbance
recovery in biomass of organisms related to:
growth rates of organisms in habitats
immigration of species adapted to new environmental conditions
adaptation of populations to new environmental conditions –
evolution
typically have recovery of community that has different species composition before
disturbance; biomass may or may not be the same as before disturbance
Press Disturbance
High
Biomass
Species Relative Abundances
100%
0%
Low
Disturbance
Time
?
10 Principles of Ecology
1. The distribution of species is limited by
barriers and unfavorable conditions
2. No population increases without limit
3. Good and poor places exist for every
species
4. Overexploited populations can collapse
5. Communities can rebound from
disturbances
10 Principles of Ecology
6. Communities can exist in several stable
configurations
7. Keystone species may be essential to a
community (species really matter)
8. Natural systems recycle essential nutrients
9. Climates change – communities change
10. Natural systems are products of evolution
But there may be a hitch….
•Human impacts on biosphere as great as any in history of earth, except
maybe evolution of photosynthetic organisms and eukaryotes
•Human impacts>>>natural stressors (faster, more intense, different)
•Now loosing more species than when dinosaurs went extinct
•Projected change in climate faster than any time in recorded history
•Doubling CO2 and increasing temperatures by 4 C in < 50 years
•Flood coastal cities (where most people are)
•Change climate and organismic distribution latitudinally
•Alter ecological interactions (CO2 effects)
•Global habitat alteration, mercury and N deposition, UV exposure
•Puts earth on new successional trajectory
Predictable Responses in Ecosystems (?)
• Odum paper, “classic” to develop
understanding dynamics of ecological
systems
• Odum – consider strategy of ecosystem
development (response after disturbance)
– Stressed ecosystems constrained, like young
ecosystems (whether toxic or enriched)
• Management of ecosystems should consider
the forces driving ecosystem development
EPA - Biological Changes along
Gradients of Human Disturbance
RA Nat. Taxa
% Nat. Taxa
% Sens. Taxa
% Tol. Taxa
Ecosys. Func.
Struc. Integrity
Func. Integrity
5
5
4
5
3
4
2
3
1
2
0
1/0
high
Pris. Ref.
Stressor Gradient
Why Sustain Natural Ecosystems?
Sustaining Ecosystems preserves Biodiversity
Biodiversity
important in adaptation of communities to stress
greater species pool facilitates changes in community
composition that will sustain ecosystem function
gene bank for species adaptation to environmental change
(evolution)
rare plants may be future crop plants with global change
genes may code for valuable proteins for medical purposes
Moral/religious reasons, humans do not have the right to
destroy other forms of life on earth (and elsewhere?)
Ecosystem Services
• Purification of air and water
• Mitigation of droughts and floods
• Generation and preservation of soils and
renewal of their fertility
• Detoxification and decomposition of wastes
• Pollination of crops and natural vegetation
• etc.
Value of Ecosystem Services
• For all Biomes (Open oceans, wetlands, forests,
grasslands, etc)
– Determine Value of all Ecosystems Services for all
Biomes
– Determine Global Area of Each Biome
– ValueBiome x Global Area Biome
– Sum Products of Value x Area for all Biomes
• $33 (16-54) trillion yr-1
• Costanza et al. 1997. Nature 387:253-260.