Ecosystems & Biodiversity
BBAEV 10201
Structure of Biosphere
• Hierarchy
– Species – reproductive group
– Population – members of a single species that
live in ...
Main Ecosystems:
•
•
•
•

Desert
Rainforest
Ocean
Taiga

•
•
•
•

Tundra
Chaparral
Grassland
Temperate Forest
Green: Grassland Purple: Taiga Orange: Tundra Black:
Temperate Forest Yellow: Desert Brown: Chaparral White:
Ocean

Geogra...
Organisms of Ecosystems
• Abiotic : Nonliving physical factors of an
environment. It includes water, oxygen,
temperature, ...
YOU TRY!!!
• List three more examples of
Abiotic & Biotic Factors:
Second Law of Thermodynamics
• There is a tendency for numbers and quantities of
biomass and energy to decrease along food...
Ecosystem: Trophic levels
Pyramid of biomass
Bio=life
Mass=weight
Bio + Mass =
Weight of living
things within an
ecosystem.
The Trophic Pyramid:
A Model of Consumption
Water cycle: More of physical process than chemical
Carbon cycle: biogeochemical process
– Recent studies indicate that human
activities have approximately doubled the
worldwide supply of fixed nitrogen, due
to ...
• Accelerated pollution of lakes.
– Human intrusion has disrupted freshwater ecosystems
by what is called cultural eutroph...
Biological and geologic processes move nutrients between
organic and inorganic compartments
Human population disrupts chemical cycles
• Human activity intrudes in nutrient cycles by
removing nutrients from one part...
In agricultural ecosystems, a large amount of
nutrients are removed from the area in the crop
biomass.
• After awhile, the...
Decomposition rates largely determine the rates of
nutrient cycling
• The rates at which nutrients cycle function in
ecosy...
Nutrient cycling is
strongly regulated by
vegetation.
Measurements (Co2 & Temp) in 1958 read 316 ppm and
increased to 370 ppm today
Human activities deplete atmospheric
ozone
• Life on earth is protected from the damaging
affects of ultraviolet radiation...
• Probable Reasons for destruction of ozone layer:
– Accumulation of chlorofluorocarbons, chemicals used in
refrigeration ...
Burning fossil fuel: Cause of acid
precipitation
• The burning of
fossil
fuels
releases
sulfur
oxides and nitrogen
that
re...
Toxins concentration in successive trophic
levels of food webs
• Humans produce many toxic chemicals that are dumped
into ...
DDT is a colourless,
crystalline, tasteless and
almost odorless
organochloride known for
its insecticidal properties
Balance
• Ecosystem will fail if it do not remain
in balance.
• No community can carry more
organisms than its food, water...
Four Scientific Principles of
Sustainability
How do they stay balanced?
•
•
•
•

Adaptation
Migration
Extinction
Give examples on each of the above?

• Provide your th...
Biodiversity
Why Is It Important?
• The biodiversity found in genes, species,
ecosystems and ecosystem processes is vital to
sustaining...
Natural Capital: Major Components of
the Earth’s Biodiversity
Biodiversity over time - geologic
• Natural changes due to new species evolving
and becoming extinct
• Extinction events –...
Genetic Makeup of a Population
• Populations evolve by becoming genetically
different
• Genetic variations is the First st...
Try this…
• Can a fish species willfully grow
limbs and fingers if they are
needed to crawl out of the water
onto dry land...
Individuals in Populations
Beneficial Genetic Traits

with

• Natural selection: Second step in biological evolution
– Ada...
A group of bacteria,
including genetically
resistant ones, are
exposed to an
antibiotic

Normal
bacterium

Resistant
bacte...
Three Common Myths about
Evolution through Natural Selection
• “Survival of the fittest” is not “survival of the
strongest...
Charles Darwin

There is a grandeur to this view of life (evolution)
While this planet has gone cycling on…
Endless forms ...
Geologic Processes
Selection

Affect

Natural

• Tectonic plates affect evolution and the location of life on
earth
– Loca...
225 million years ago

65 million years ago

135 million years ago

Present
Climate Change and Catastrophes
Affect Natural Selection
• Ice ages followed by warming temperatures
Demise of the giants ...
Changes in Ice Coverage in the Northern
Hemisphere During the last 18,000 Years
Science Focus: Earth Is Just Right
for Life to Thrive
• Certain temperature range (closeness to sun)
• Dependence on water...
What does Evolution mean to
you?
Evidence?
The Fossil Record Tells Much of
the Story of Evolution
• Fossils
– Physical evidence of ancient organisms
– Bones, casts, ...
Fossilized Skeleton of an
Herbivore that walked the Earth
Questions
Q1) What is the connection
environment and evolution?

between

the

Q2) Will humans evolve to a point where we ...
How Do Speciation, Extinction, and
Human Activities Affect Biodiversity?
• As environmental conditions change, the balance...
Evolution
• Through geographic isolation
– Groups of same species become physically
isolated
– Migration, physical barrier...
Geographic Isolation Can Lead to
Reproductive Isolation
Science Focus: Humans Have Two Ways to Change
the Genetic Traits of Populations

• Artificial selection
• Genetic engineer...
Genetically Engineered Mice
Animation: Transferring genes
into plants
Species Diversity its Importance
• A major component of biodiversity
– Species richness (diversity in species)
– Species e...
Variations in Species Richness
Variation in species evenness
• Temperate Forest, Western Ghats, chilka lake
Species-Rich Ecosystems Tend
to Be Productive and Sustainable
• Species richness seems to increase
productivity and stabil...
What Roles Do Species Play in
Ecosystems?
• Each species plays a specific ecological role
called its niche.
• Any given sp...
Role of Keystone, Foundation
Species
• Keystone species
– Pollinators
– Top predator( Sharks, Tigers)
– Loss of keystone s...
Species Plays a Unique Role
in Its Ecosystem
• Ecological niche
– Pattern of living, includes everything that affects
surv...
Specialist Species and Generalist
Species Niches
Case Study: Cockroaches:
Nature’s Ultimate Survivors
• Cockroaches
– Generalists
– High reproductive rates
• 10 million an...
Threats to Biodiversity:
Why Are Amphibians Vanishing?
• Habitat loss and fragmentation
• Prolonged drought
• Pollution
• ...
Impact of Vanishing Amphibians
• Importance of amphibians
– Sensitive biological indicators of environmental
changes
– Adu...
Case Study: Why Should We
Protect Sharks?
• Keystone species
– Eat dead and dying fish in the ocean
– Control other popula...
Case Study: Is the Royal Bengal
Tiger worth saving?

Project tiger:

Launched in 1973 by GoI and WWF with 9 tiger reserves...
Reflect on these!

Source: Wildlife protection society of India

TIGER DEATHS IN 2014
Mortality
6
Poaching &
Seizures
1
__...
Why are Tigers important?
• Keystone species
• Presence in food web
• Pathways- keep pathways open, hold back
changes in m...
Humans: Saviour or Threat to
biodiversity
• Present day rates exceed geological rates of
extinction. Scientists est. that ...
Extinction of
large mammals
and birds
corresponds to
the spread of
human
populations
Parks & Sanctuaries
Almost 4 % of India's land is under forests. There are 80 national parks and over 441
wildlife sanctua...
Case Study: Beej Bachao Aandolan (Save the
seed Movement) & livestocks breeding
• Seed Movement began in Himalayan tarai
•...
Questions?
Q1) Distinguish between species richness and evenness
Q2) Suppose we have 2 national parks close to each other
...
Project Questions
1. Are there regions of your country with large amounts of
biodiversity?
2. What climate conditions/Geol...
Questions
• Q1: What are three ways that the Tigers supports one or more
of the four components of biodiversity within its...
Deforestation and soil nutrients
• Distinct differences in storage of biomass &
nutrient cycling between temperate & tropi...
Tropical above ground
storage of biomass & nutrients
Deforestation and recovery
• Rainforests – loss of rainforest trees leads to
loss of nutrients & changes in the water
cycl...
Deforestation & water cycle & climate
• Elimination of tropical rainforests disrupts regional
water cycle
– Minimizes evap...
Biodiversity and deforestation in tropical
areas
• Half of the living species are found in rainforests
• Forest plants hav...
Biodiversity and ecosystem stability
• Relationship is complex
– In some settings environmental stability leads to high
di...
Causes of deforestation
• Social, political, and economic drivers
• Economic arguments – people and countries
need hard cu...
Ecosystems and biodiversity
Ecosystems and biodiversity
Ecosystems and biodiversity
Ecosystems and biodiversity
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  • Figure 4.5
    Evolution by natural selection. (a) A population of bacteria is exposed to an antibiotic, which (b) kills all but those possessing a trait that makes them resistant to the drug. (c) The resistant bacteria multiply and eventually (d) replace the nonresistant bacteria.
  • Figure 4.6
    Over millions of years, the earth’s continents have moved very slowly on several gigantic tectonic plates. This process plays a role in the extinction of species, as land areas split apart, and also in the rise of new species when isolated land areas combine. Rock and fossil evidence indicates that 200–250 million years ago, all of the earth’s present-day continents were locked together in a supercontinent called Pangaea (top left). About 180 million years ago, Pangaea began splitting apart as the earth’s tectonic plates separated, eventually resulting in today’s locations of the continents (bottom right). Question: How might an area of land splitting apart cause the extinction of a species?
  • Ecosystems and biodiversity

    1. 1. Ecosystems & Biodiversity BBAEV 10201
    2. 2. Structure of Biosphere • Hierarchy – Species – reproductive group – Population – members of a single species that live in a given area – Community – assemblage of interacting species in a given area – Biome – a region with a characteristic plant community (e.g. rainforest, desert) – Ecosystem – a community of animals, plants, microbes, etc. together with the physical environment that supports it
    3. 3. Main Ecosystems: • • • • Desert Rainforest Ocean Taiga • • • • Tundra Chaparral Grassland Temperate Forest
    4. 4. Green: Grassland Purple: Taiga Orange: Tundra Black: Temperate Forest Yellow: Desert Brown: Chaparral White: Ocean Geography, weather, climate and geologic factors influences interactions within an
    5. 5. Organisms of Ecosystems • Abiotic : Nonliving physical factors of an environment. It includes water, oxygen, temperature, amount of sunlight and water pressure etc. • Biotoic: Living physical factors of an environment. Examples: Parasitism, disease and predation.
    6. 6. YOU TRY!!! • List three more examples of Abiotic & Biotic Factors:
    7. 7. Second Law of Thermodynamics • There is a tendency for numbers and quantities of biomass and energy to decrease along food chains. • The pyramids become smaller at the top because around 90% of the energy is “lost” between each level and only 10% is available in the body of the organism for transfer to the next level.
    8. 8. Ecosystem: Trophic levels
    9. 9. Pyramid of biomass Bio=life Mass=weight Bio + Mass = Weight of living things within an ecosystem.
    10. 10. The Trophic Pyramid: A Model of Consumption
    11. 11. Water cycle: More of physical process than chemical
    12. 12. Carbon cycle: biogeochemical process
    13. 13. – Recent studies indicate that human activities have approximately doubled the worldwide supply of fixed nitrogen, due to the use of fertilizers, cultivation of legumes, and burning. – Possible outcome • increase nitrogen oxides in the atmosphere • Contribute to atmospheric warming • Depletion of ozone • Acid rain.
    14. 14. • Accelerated pollution of lakes. – Human intrusion has disrupted freshwater ecosystems by what is called cultural eutrophication. • Sewage and factory wastes, runoff of animal wastes from pastures and stockyards have overloaded many freshwater streams and lakes with nitrogen. • This can eliminate fish species because it is difficult for them to live in these new conditions.
    15. 15. Biological and geologic processes move nutrients between organic and inorganic compartments
    16. 16. Human population disrupts chemical cycles • Human activity intrudes in nutrient cycles by removing nutrients from one part of the biosphere and then adding them to another. • Agricultural effects of nutrient cycling.
    17. 17. In agricultural ecosystems, a large amount of nutrients are removed from the area in the crop biomass. • After awhile, the natural store of nutrients can become exhausted.
    18. 18. Decomposition rates largely determine the rates of nutrient cycling • The rates at which nutrients cycle function in ecosystems are extremely variable as a result of variable rates of decomposition. – Decomposition can take up to 50 years in the tundra, while in the tropical forest, it can occur much faster. – Contents of nutrients in the soil of different ecosystems vary also, depending on the rate of absorption by the plants.
    19. 19. Nutrient cycling is strongly regulated by vegetation.
    20. 20. Measurements (Co2 & Temp) in 1958 read 316 ppm and increased to 370 ppm today
    21. 21. Human activities deplete atmospheric ozone • Life on earth is protected from the damaging affects of ultraviolet radiation (UV) by a layer of O3, or ozone. • Studies suggest that the ozone layer has been gradually “thinning” since 1975.
    22. 22. • Probable Reasons for destruction of ozone layer: – Accumulation of chlorofluorocarbons, chemicals used in refrigeration and aerosol cans, and in certain manufacturing processes. – Increased levels of UV radiation that reach the surface of the Earth. This radiation has been linked to skin cancer and cataracts. • The impact of human activity on the ozone layer is one more example of how much we are able to disrupt ecosystems and the entire biosphere.
    23. 23. Burning fossil fuel: Cause of acid precipitation • The burning of fossil fuels releases sulfur oxides and nitrogen that react with water in the atmosphere to produce sulfuric and nitric acids.
    24. 24. Toxins concentration in successive trophic levels of food webs • Humans produce many toxic chemicals that are dumped into ecosystems. – These substances are ingested and metabolized by the organisms in the ecosystems and can accumulate in the fatty tissues of animals. – These toxins become more concentrated in successive trophic levels of a food web, a process called biological magnification.
    25. 25. DDT is a colourless, crystalline, tasteless and almost odorless organochloride known for its insecticidal properties
    26. 26. Balance • Ecosystem will fail if it do not remain in balance. • No community can carry more organisms than its food, water and shelter can accommodate.
    27. 27. Four Scientific Principles of Sustainability
    28. 28. How do they stay balanced? • • • • Adaptation Migration Extinction Give examples on each of the above? • Provide your thought on ways to balance the ecosystem in the current scenario?
    29. 29. Biodiversity
    30. 30. Why Is It Important? • The biodiversity found in genes, species, ecosystems and ecosystem processes is vital to sustaining life on earth.
    31. 31. Natural Capital: Major Components of the Earth’s Biodiversity
    32. 32. Biodiversity over time - geologic • Natural changes due to new species evolving and becoming extinct • Extinction events – cleans the slate – Natural extinction – 90% of species ever alive are extinct now
    33. 33. Genetic Makeup of a Population • Populations evolve by becoming genetically different • Genetic variations is the First step in biological evolution – Occurs through mutations in reproductive cells – Mutations in other cells can happen , but only reproductive cell mutations are passed on – Sometimes a mutation can result in a new genetic trait that gives it a better chance to survive, sometimes not.
    34. 34. Try this… • Can a fish species willfully grow limbs and fingers if they are needed to crawl out of the water onto dry land?
    35. 35. Individuals in Populations Beneficial Genetic Traits with • Natural selection: Second step in biological evolution – Adaptation may lead to differential reproduction – Genetic resistance in bacteria, cockroaches • When environmental conditions change, populations – Adapt – Migrate – Become extinct
    36. 36. A group of bacteria, including genetically resistant ones, are exposed to an antibiotic Normal bacterium Resistant bacterium Most of the normal bacteria die The genetically resistant bacteria start multiplying Eventually the resistant strain replaces the strain affected by the antibiotic
    37. 37. Three Common Myths about Evolution through Natural Selection • “Survival of the fittest” is not “survival of the strongest” • Organisms do not develop traits out of need or want • No grand plan of nature for perfect adaptation
    38. 38. Charles Darwin There is a grandeur to this view of life (evolution) While this planet has gone cycling on… Endless forms most beautiful and wonderful have been and are being evolved Can you draw similes of evolution to Corporates/ organisations?
    39. 39. Geologic Processes Selection Affect Natural • Tectonic plates affect evolution and the location of life on earth – Location of continents and oceans – Species physically move, or adapt, or form new species through natural selection • Tectonic actions: Earthquakes, Volcanic eruptions can have profound effects on natural selection – Pollution – Change in ecosystem
    40. 40. 225 million years ago 65 million years ago 135 million years ago Present
    41. 41. Climate Change and Catastrophes Affect Natural Selection • Ice ages followed by warming temperatures Demise of the giants (Sloth, Saber tooth tigers) • Collisions between the earth and large asteroids – New species – Extinction
    42. 42. Changes in Ice Coverage in the Northern Hemisphere During the last 18,000 Years
    43. 43. Science Focus: Earth Is Just Right for Life to Thrive • Certain temperature range (closeness to sun) • Dependence on water • Rotation on its axis (how fast or slow we spin) • Revolution around the sun (changes in season) • Enough gravitational mass (to hold on to the atmos)
    44. 44. What does Evolution mean to you? Evidence?
    45. 45. The Fossil Record Tells Much of the Story of Evolution • Fossils – Physical evidence of ancient organisms – Bones, casts, tracks… – Some reveal what their internal structures looked like, some their actions • Have all fossils been discovered?
    46. 46. Fossilized Skeleton of an Herbivore that walked the Earth
    47. 47. Questions Q1) What is the connection environment and evolution? between the Q2) Will humans evolve to a point where we can survive in space without a spacesuit or any protective device? Why or Why not? Q3) how does pollution effect evolution?
    48. 48. How Do Speciation, Extinction, and Human Activities Affect Biodiversity? • As environmental conditions change, the balance between formation of new species and extinction of existing species determines the earth’s biodiversity. • Human activities can decrease biodiversity by causing the premature extinction of species and by destroying or degrading habitats needed for the development of new species.
    49. 49. Evolution • Through geographic isolation – Groups of same species become physically isolated – Migration, physical barriers (volcanoes) • Through reproductive isolation – Mutation and change by natural selection occur in isolated geographic populations long enough – New species when interbreeding produces only sterile offspring
    50. 50. Geographic Isolation Can Lead to Reproductive Isolation
    51. 51. Science Focus: Humans Have Two Ways to Change the Genetic Traits of Populations • Artificial selection • Genetic engineering, gene splicing • Consider – – – – Ethics Morals Privacy issues Harmful effects
    52. 52. Genetically Engineered Mice
    53. 53. Animation: Transferring genes into plants
    54. 54. Species Diversity its Importance • A major component of biodiversity – Species richness (diversity in species) – Species evenness (abundance of each species) • Diversity varies with geographical location – Most species-rich communities • • • • Tropical rain forests Coral reefs Ocean bottom zone Large tropical lakes • Increases the sustainability of ecosystems.
    55. 55. Variations in Species Richness
    56. 56. Variation in species evenness • Temperate Forest, Western Ghats, chilka lake
    57. 57. Species-Rich Ecosystems Tend to Be Productive and Sustainable • Species richness seems to increase productivity and stability or sustainability of a location • More diverse ecosystem, more productive, greater biomass • More diverse, more complex web, more resistant to environmental disturbances
    58. 58. What Roles Do Species Play in Ecosystems? • Each species plays a specific ecological role called its niche. • Any given species may play one or more of five important roles—native, nonnative, indicator (defines traits of environment), keystone, or foundation roles—in a particular ecosystem.
    59. 59. Role of Keystone, Foundation Species • Keystone species – Pollinators – Top predator( Sharks, Tigers) – Loss of keystone species lead to population crashes of other species in ecosystem • Foundation species – Create or enhance their habitats, which benefit others • Elephants (trails)
    60. 60. Species Plays a Unique Role in Its Ecosystem • Ecological niche – Pattern of living, includes everything that affects survival and reproduction • Generalist species (mice, humans, raccoons) – Broad niche • Specialist species (Tigers, pandas) – Narrow niche
    61. 61. Specialist Species and Generalist Species Niches
    62. 62. Case Study: Cockroaches: Nature’s Ultimate Survivors • Cockroaches – Generalists – High reproductive rates • 10 million annually – Eat almost anything: – Finger nail clippings, electric cords, soap – Live and breed in all but arctic environ – Antennae, knee joints, eyes Good: food for higher order consumers
    63. 63. Threats to Biodiversity: Why Are Amphibians Vanishing? • Habitat loss and fragmentation • Prolonged drought • Pollution • Increase in UV radiation • Parasites (worms causing increase in birth defects) • Viral and fungal diseases • Climate change • Overhunting (Asia and France) • Nonnative predators and competitors
    64. 64. Impact of Vanishing Amphibians • Importance of amphibians – Sensitive biological indicators of environmental changes – Adult amphibians • Important ecological roles in biological communities – Genetic storehouse of pharmaceutical products waiting to be discovered
    65. 65. Case Study: Why Should We Protect Sharks? • Keystone species – Eat dead and dying fish in the ocean – Control other populations – Strong immune systems • Wounds do not get infected • Almost never get cancer • Could help humans if we understood their immune system
    66. 66. Case Study: Is the Royal Bengal Tiger worth saving? Project tiger: Launched in 1973 by GoI and WWF with 9 tiger reserves having 268 tigers. In 2001, tiger reserves increased to 27, # of tigers ~1500!!. In 2011, we have 53 tigers reserves. Latest tiger census report released in 2011 by the National Tiger Conservation Authority, est. tiger population is 1,706. Your observation?
    67. 67. Reflect on these! Source: Wildlife protection society of India TIGER DEATHS IN 2014 Mortality 6 Poaching & Seizures 1 ___________________ Total 7 LEOPARD DEATHS IN 2014 Mortality 17 Poaching & 12 Seizures ___________________ Total 29 TIGER DEATHS IN 2013 Mortality 38 Poaching & 42 Seizures ___________________ Total 80 LEOPARD DEATHS IN 2013 Mortality 217 Poaching & 110 Seizures ___________________ Total 327 A tigress believed to have strayed from Jim Corbett National Park, killed its 10th person in six weeks. Source: CBC News: Feb 10’14. The tiger has been on the prowl across an area spanning some 130 kilometres. "The animal has started attacking humans because it is not getting its natural prey," said Rupek De, chief wildlife warden of Uttar Pradesh. •Jumbo concern only gets bigger - In six years, 354 persons killed by elephants in state Orissa, 5 th Dec., 2013 •Huge number of seized leopard claws puzzles Forest officials, 6th Dec., 2013
    68. 68. Why are Tigers important? • Keystone species • Presence in food web • Pathways- keep pathways open, hold back changes in marshy areas • Maintain Ecological Balance – Provide in-situ conservation (protect its habitat with all other species). Create national Parks & Sanctuaries – Establish ex-situ conservation (for endangered species give protection in controlled environment viz. botanical garden for plants & zoological parks for animals)
    69. 69. Humans: Saviour or Threat to biodiversity • Present day rates exceed geological rates of extinction. Scientists est. that we are likely to eliminate ~ 10Million species by 2050 • Present day extinction is across the board – affects many groups • Modern extinction associated with spread of human populations – Over hunting/fishing – Habitat destruction – deforestation & coral bleaching
    70. 70. Extinction of large mammals and birds corresponds to the spread of human populations
    71. 71. Parks & Sanctuaries Almost 4 % of India's land is under forests. There are 80 national parks and over 441 wildlife sanctuaries in India. •National Park: •National parks are formed by Central or State Legislation. •Status of National Park is higher. •No human habitation is permitted in the park area. •Harvesting timbers, cultivation, collection of forest products are restricted. Eg. Corbet National Park. •Sanctuary: •Sanctuaries are formed by the order of State or Central Government. •Status of sanctuary is lower. •Private ownership may be allowed. •Limited activities are allowed with permission. Eg. ChilikaSanctuary for migrating birds.
    72. 72. Case Study: Beej Bachao Aandolan (Save the seed Movement) & livestocks breeding • Seed Movement began in Himalayan tarai • Successfully conserved hundreds of local rice varieties. • Gene banks collected 34000 cereals & 22000 pulses grown in India • 27 breeds of cattle &goats, 8 breeds of buffaloes. Many are dying out due to misguided adoption of ‘foreign’ things viz: Jerseys & Holsteins
    73. 73. Questions? Q1) Distinguish between species richness and evenness Q2) Suppose we have 2 national parks close to each other surrounded by development. One is a large park and the other much smaller. Which park is likely to have the highest species richness? Why?
    74. 74. Project Questions 1. Are there regions of your country with large amounts of biodiversity? 2. What climate conditions/Geologic features have influence on natural selection in the major biomes of your country? 3. Indicate some unique indicator, keystone, foundation, invasive and specialist species that live within the borders of your country? 4. Do the people in your country get most of their food from within ? Substantiate your answer with examples.
    75. 75. Questions • Q1: What are three ways that the Tigers supports one or more of the four components of biodiversity within its environment? • Q2: What are three examples of how people, in their daily living, intentionally or unintentionally degrade each of these types of biodiversity? • Q3: What are the main differences between Functional and Ecological Diversity? What are the main differences between species and genetic diversity? • Q4: Why is having a lot of biodiversity on earth so beneficial to us?
    76. 76. Deforestation and soil nutrients • Distinct differences in storage of biomass & nutrient cycling between temperate & tropical forests • Temperate forests have thick, rich topsoils – Humus layer of organic detritus on top of subsoil – Nutrients stored in soils • Tropical soils are highly weathered (lots of rain) – Lateritic clays depleted in nutrients – Thin humus layer – Nutrients stored in biomass
    77. 77. Tropical above ground storage of biomass & nutrients
    78. 78. Deforestation and recovery • Rainforests – loss of rainforest trees leads to loss of nutrients & changes in the water cycle • Temperate forests recover because nutrients retained in the soils
    79. 79. Deforestation & water cycle & climate • Elimination of tropical rainforests disrupts regional water cycle – Minimizes evapotranspiration (source of H2O to atm) – Decreases soil moisture and increases runoff • Increases erosion rates – Soils form slowly – 200-1500 yrs to form 2.5 cm of topsoil from bedrock • General circulation models to predict – Net temperature increase – Decrease in soil moisture
    80. 80. Biodiversity and deforestation in tropical areas • Half of the living species are found in rainforests • Forest plants have medical value – Treatment of diseases • Forest plants have agricultural value – Need genetic diversity for long-term health (Darwinian evolution) – Need variety to limit vulnerability to diseases and pests – Modern agricultural practices limit diversities – Centers of genetic diversity for crops come from areas threatened by development, population pressures, deforestation – Seed banks
    81. 81. Biodiversity and ecosystem stability • Relationship is complex – In some settings environmental stability leads to high diversity – In others, high diversity is thought to result from disturbances of intermediate frequency and intensity • How does loss of biodiversity impact ecosystem? – Remove enough species and ecosystem collapses (removal of predators; invasive species) – May be that some species aren’t necessary – system maintained by a few keystone species
    82. 82. Causes of deforestation • Social, political, and economic drivers • Economic arguments – people and countries need hard currency (Nepal) – Motivation not to – Who will bear the costs of not exploiting resources? • Earth will recover, will humans survive?
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