Human Impact on Ecosytems Chapter 16

Human Population Growth and Natural Resources Human Population Growing Thomas Malthus Essay Human Population cannot grow forever Claimed population was growing faster than resource production 1700’s – 1 billion Now - ~6 billion Carrying capacity?

Human Population Growth and Natural Resources Technology and Population Growth How has technology affected: Agriculture Medicine Sanitation Transportation Is this all a good thing? Carrying capacity changes as the environment changes Gas powered farm equipment allows for the production of mass quantities of food In 1940 20 infants per 1000 births died – in 2002 7 per 1000 This is due to better medicine and better sanitation Food and products are moved more easily now with transportation

Human Population Growth and Natural Resources Population Growth and Resources Two major energy resources Oil Coal Renewable energy resources Wind Solar Drinking water Oil and coal are non-renewable resources – used faster than they are formed 2006 – humans used about 77 million barrels per day Keystone XL Transcanada oil project-pipileine that would run from Alberta, CA to Steele City, NE – Hundereds of thousands of barrels of oil per dayM Renewable resources are not used as fast as they are produced

Human Population Growth and Natural Resources Management of Resources Easter island Inhabited around 400-700 A.D. Population grew over next 1000 years Harvested trees faster than they could regrow Animal populations destroyed, soil washed away Human population crash

Human Population Growth and Natural Resources Ecological Footprint Amount of land needed to maintain enough food, water, and shelter Dependent upon efficient use of resources Developing countries Footprint getting bigger in developing countries, but so is population U.S. has big footprint, but other countries have more “feet”

Air Quality Pollutants Human activity directly and indirectly effect Earth Smog and Ozone Acid Rain Creates pollution Any undesireable factor added to the atmosphere

Air Quality Smog and Ozone Most common air pollution comes from human activities Burning fossil fuels causes chemicals to recombine forming pollutants Smog – sunlight interacting with pollutants Particulates can be inhaled causing health problems Ozone – Nitrous oxide interacts with ground level oxygen giving ozone Most common is burning fossil fuels Ozone can be harmful to asthmatics and people with breathing problems, but is a big part atmosphere

Air Quality Acid rain Chemicals from fossil fuels can also interact with rain Cause the pH to drop Normal rain is slightly acidic – 5.6 With emissions can drop below that Can cause declines in growth rates and also break down of bark

Air Quality Greenhouse Effect Sunlight Greenhouse gases Some is absorbed by atmosphere Some gets to Earth’s surface This is radiated as infrared heat Greenhouse gases Create a blanket and insulate the Earth Gases – Water vapor, methane gas, carbon dioxide

Air Quality Global Warming Temperature rising – 0.6 degrees C over last 100 years Due to increased concentrations of greenhouse gases Disagreement on the impact of humans Creating increased flooding, stronger storms, melting ice caps

Water Quality Water Pollution Chemicals can contaminate water supplies Raw sewage Farm runoff Algae build up Scientists study indicator species Provides a sign as to the quality of an ecosystem’s conditions Algae can reduce dissolved oxygen levels-this can lead to a reduction in breakdown by detrivores This leads to a buildup in ponds and lakes called eutrophication Gender bending fish-traces of female hormones have been found in lakes from human medications-fish starting to change from male to female

Water Quality Biomagnification Movement of toxins up the food chain Causes an accumulation of the toxin in predators Organisms at higher trophic levels eat more organisms which causes increases in toxicity Has greatest effect on species at top of food chaing Many chemicals are fat soluble meaning they stay in the body of an organism When that organism is eaten the predator gets everything that is trapped in the organism This could start as low as phytoplankton and move up through the chain

Threats to Biodiversity Loss of Biodiversity Loss of habitat and pollution Effects plant and animal species Losing species directly affects humans Almost half the prescribed medicines come from plants Technological advances often start in nature Loss of a single species can have a rippling effect Some scientists use what they see in nature for creating new technology – mussels and adhesives Sri Lanka – 95% of their rainforests are gone-this has caused 19 species of frogs to go extinct

Threats to Biodiversity Habitat Loss Humans are moving into wilderness areas Causing a loss of animal habitat Between 1780-1980 53% of wetlands lost Many migrating bird species lost Habitat Fragmentation Barrier forms preventing a species from access to entire home range Fragmentation is caused by building roads or harvesting forests which prevents the species from accessing the entire ecosystem Create wildlife overpasses

Threats to Biodiversity Introduced (Invasive) Species Species introduced to an ecosystem by human activity Can threaten native species Can lead to economic damage Often times exploit a new niche Is a better competitor than native species

Threats to Biodiversity 10 worst invasive species Kudzu Rabbits Starlings Burmese pythons Cane toads Snakehead fish Gray squirrels Killer bees Asian carp Rats

Threats to Biodiversity Native Species effects Invasive species can cause threaten species to become extinct Burmese python

Threats to Biodiversity Economic Impact House mice Exponentially increase every 4-5 years Rainy seasons increase crop production This in turn increases mice populations Creates crop damage

Conservation Sustainable Development Resources are used in a responsible manner Ensures future generations have resources Methods of harvesting and foresting Sustainable fisheries Rotation Fishing gear Harvest reduction Fishing bans Rotation – rotate catches between different species giving off species time to recover Fishing gear – using gear that minimizes unintentional catches; reduces damage to sea floor and reefs Harvest reduction – slow the harvest of deep water species that grow much slower allowing time for recovery Fishing bans – banning fishing areas and species to allow for recovery of certain species

Conservation Species Protection Endangered Species Act Protects species near extinction and its habitat Often benefits other species – Umbrella Species Protection of one species provides benefits to other species Ex. Manatees Northern spotted owls and old growth forest : ex. Molluscs and salamanders are within the protective boundaries of the northern spotted owl. Bay checkerspot butterfly and grasslands Tigers in India and elsewhere. Project Tiger was launched to save the tiger and thereby its habitat and other species within it. Manatee protection includes a large area from Florida to Texas-protection of sea grass-only 3000 manatees exist

Conservation Importance of Resources Protection has both practical and economic benefits Medications come from ecosystems Nutrients cycle through Value of resources is approximately $30 trillion Threatened by global warming, pollution, and loss of biodiversity

Conservation Protecting Resources Environmental Protection Act (EPA) Established in 1970 Develop polices and laws to protect the environment Created such laws as: Clean Water Act Clean Air Act Endangered Species Act Grants for National Parks

Conservation Sustainable Earth Humans have the greatest impact on resources Control the use How fast populations grow Develop technologies to produce more food Ability to change practices regarding forestry, fishing, harvesting No where on Earth is exempt from human interaction