Impacts of Humans on Ecosystems

Impacts of Humans on Ecosystems

Objectives • G.3.11 – State that ozone in the stratosphere absorbs ultraviolet (UV) radiation. • G.3.9 –- Outline the effects of UV radiation on living tissues and biological productivity. • G.3.10 – Outline the effects of chlorofluorocarbons (CFCs) on the ozone layer. • G.3.7 –- Define biomagnification. • G.3.8 –- Explain the cause and consequences of biomagnification, using a named example.

Impacts of Humans on Ecosystems The Ozone Hole

Stratospheric ozone Review earth science: Stratosphere • 7 – 30 miles above sea level. • Ozone layer.

Stratospheric ozone Ozone in the stratosphere absorbs ultraviolet (UV) radiation. • UV radiation is energy that can break chemical bonds in molecules such as DNA causing mutations, which lead to cancer. • Three types of UV radiation: UVA, UVB, UVC. • UVA has the longest wavelength & is least energetic.

Stratospheric ozone Ozone in the stratosphere absorbs UV radiation. • Ozone forms when radiation or electrical discharge separates the two atoms in an oxygen molecule (O2), which can then individually recombine with other oxygen molecules to form ozone (O3). Some UVA is absorbed in the formation of ozone. Some UVB is absorbed in the destruction of ozone.

Stratospheric ozone Ozone in the stratosphere absorbs UV radiation. • Some UVA is absorbed in the formation of ozone. • Some UVB is absorbed in the destruction of ozone. Most of the UV that reaches the ground is the less dangerous UVA.

Effects of UV radiation Life on Earth remained microscopic until development of free oxygen in the atmosphere ~3.4 billion yrs ago • Thereafter, life remained in the ocean until the ozone layer formed. Life washed out was fried by UV light. • Only after the ozone layer formed ~600 million yrs ago could life move onto the land.

Effects of UV radiation

Effects of UV radiation Direct human health effects: • Suppression of immunity leads to more disease. • Eye damage – cataracts & blindness.

Effects of UV radiation Direct human health effects: • Both UVA & UVB rays damage skin. • Sunburn is a sign of short-term overexposure. • Premature aging* & skin cancer are side effects of prolonged exposure. UVA penetrates deeper *Collagen fibers are weakened.

Effects of UV radiation Direct human health effects: • Skin cancer • UVB does more damage to skin, but most blocked by clouds, clothing, glass. • UVA is greatest threat – penetrates to living skin cells and damages DNA. The ABCD’s of skin cancer.

Effects of UV radiation Direct human health effects: • Skin cancer • Sunscreens – SPF – Sun Protection Factor – Time needed to produce a sunburn on protected skin relative to time needed to produce a sunburn on unprotected skin. If it normally takes 20 minutes to burn, SPF 2 doubles time to 40 minutes. SPF 15 or above is considered best.

Effects of UV radiation Damage to biological links in the food chain: • UV kills ocean plankton, leads to reduced fish harvests. • Stunted plant growth reduces crop yields. Sunburned leaves

Effects of CFCs on the ozone layer Human activities are depleting atmospheric ozone. Chlorofluorocarbons (CFCs) destroy ozone, creating an “ozone hole” over parts of the earth. Areas beneath the ‘hole” are more prone to UV radiation.

Effects of CFCs on the ozone layer Human activities are depleting atmospheric ozone. One chlorine or bromine molecule can destroy 100,000 ozone molecules, causing ozone to disappear much faster than nature can replace it.

Biomagnification Biomagnification is the increase in concentration of a chem-ical as it passes from one level in a food chain to the next • This occurs because the chemical is fat soluble and not excreted in the urine, or it is not degraded. • Since creatures at high trophic levels must eat a lot of lower- level creatures, chemicals build up in them.

Biomagnification DDT in the food chain • DDT – a pesticide to kill mosquitoes and other insects. • Used to reduce insect-borne disease like malaria. • Poisons accumulate in creatures at the top of the food chain.

Biomagnification DDT in the food chain • The chemical builds up in predatory birds and affects their ability to form a shell around their eggs. The eggs are crushed during incubation, and the bird population drops (ex: the California condor). By 1987 there were fewer than 30 condors. Today there are >100.

Biomagnification Mercury in the food chain • Source: industry and agricultural pesticide. • Bacteria convert inorganic Hg to methylmercury.

Biomagnification Mercury in the food chain • Methylmercury builds up in fatty tissues. • Accumulates from <1 ppb to over 5000 ppb in large fish.

Biomagnification Mercury in the food chain • Impacts:

Biomagnification Beware of what you eat.

Impacts of Humans on Ecosystems

Objectives • Fl.17.16 – Discuss the environmental impacts resulting from human activity. • Fl.17.11 – Compare costs and benefits of renewable and nonrenewable resources. • Fl.17.12 – Discuss consequences of sustainable land use. • Fl.17.8 – Discuss reasons for conservation of biodiversity • Fl.17.13 – Discuss the need for environmental monitoring • Fl.17.14 – Assess the need for adequate waste disposal. • Fl.17.15 – Discuss effects of technology on environmental quality. • Fl.HE.13 – Evaluate how environmental and personal health are interrelated.

Earth is an island We have limited resources on the planet.

Earth is an island Humans have changed the planet through… • Agriculture, industry, technology, overpopulation

Earth is an island Sustainable land use • Over-grazing of live- stock, excessive agriculture, overpopulation strip land of its regenerative ca- pacity, and it can no longer sustain life. Desertification

Earth is an island As non-renewable resources (coal, oil) become scarcer, renewable resources* become less costly, non-pollut- ing alternatives. *Hydro, solar, wind, geothermal energy

Earth is an island We don’t recycle enough!

The biodiversity crisis Extinctions have occurred since life began on Earth, but the current high rate, accelerated by humans, creates a crisis.

The biodiversity crisis Ecological threats to biodiversity. Habitat destruction (and fragmentation): • Responsible for 73% of endangered species. • Rainforest cut for logging, then used for agriculture Introduced species: • Those that humans moved from native locations to new geographic regions. • Australian melaluca trees in Florida out- compete native plants. • Pythons in the Everglades eat natives’ food. • Dogs & cats also compete for food of natives. • Snakes on Guam eat eggs of native birds. • Goats, sheep, cattle change the ecosystem.

The biodiversity crisis Habitat destruction: Life that is considered to be “less important” is often pushed aside in the name of Development. Haiti Dominican Republic

The biodiversity crisis Introduced species are those that humans have moved from native locations to new geographic regions. • They generally upset food webs by adding new predators (includes pathogens) or competitors. The cat disturbs the food web.

The biodiversity crisis Accidental introduction into Florida • Burmese python into the Everglades • Escaped pets (or abandonment) • Eat rodents & larger animals (young gators) - prey of Florida panthers (could eat them, too.)

The biodiversity crisis Intentional introduction into Florida • The Australian melaluca tree • Originally (1875 – 1900) planted as a windbreak and to control erosion around levees, then by developers to dry up the Everglades for housing. • Out-competes other plants for light » less diversity.

The biodiversity crisis Species extinction • Humans (aliens to most of the planet) are causing major extinctions planet-wide. • Over-hunting of passenger pigeons and dodo birds. • Wild, formerly-domesticated goats & pigs are killing native Hawaiian plants & birds.

The biodiversity crisis The U.S. Endangered Species Act defines: • Endangered species as one in danger of extinction throughout its range • 993 species in the US • 71 species listed in Florida • Florida panther • West Indian manatee • Threatened species as one likely to become endangered in the foreseeable future.

The biodiversity crisis Ecological consequences 1) Loss of genetic diversity: If a local population dies out, genes could disappear that might help the species adapt to new environmental conditions, such as global warming. 2) Loss of species diversity: A species may be critical to another 3) Loss of ecosystem diversity: Loss of a pattern of energy flow - a food chain or food web disrupted

The biodiversity crisis Loss of ecosystem diversity: Pine rock- lands of S. Florida: • Loss of 98% due to development • Fragmentation of habitats

The biodiversity crisis Economic threats to biodiversity Overexploitation • Harvesting of wild plants & animals at rates that exceed the ability of those populations to rebound. • Tropical woods for furniture (generations to repopulate) • Tropical birds, reptiles, orchids are taken for sale. • Hunting as a sport or for food

The biodiversity crisis Economic consequences • Some lost species may have provided new food sources or medicines. • Many cancer drugs are botanicals. • Plants can be sources of synthetic fuels and foods.

Conservation of Biodiversity Reasons for the conservation of biodiversity: • Ecological • Economic • Aesthetic • Ethical

Conservation of biodiversity Ecological advantages of conservation • Preserving genetic, species, & ecosystem diversity. • All help to maintain stable ecosystems (food, water).

Conservation of Biodiversity Economic advantages of conservation • Maintaining US parklands can provide jobs for rangers, vendors, amusement operators (guides, ski lifts, boat docks, etc.). Forests provide income from sustainable logging. Old Faithful, Yellowstone National Park

Conservation of Biodiversity Economic advantages of conservation • Eco-tourism brings tourists and money both within and outside the US. • Ex: Costa Rican rainforest

Conservation of Biodiversity Aesthetic reasons for conservation • Nature can be beautiful and peaceful - a respite from the daily grind and modern technology - and… • Inspirational Yosemite National Forest

Conservation of Biodiversity Ethical reasons for conservation • What right do humans have to disturb life for the other inhabitants of earth and to presume our needs are most important?

Conservation of Biodiversity Ethical reasons for conservation • It is wrong to take and take and take until there is little more than people on the face of the planet. Coruscant

Conservation US stamps – specific taxes that support conservation

Impacts of Humans on Ecosystems