Sources and Sinks Sources or Supply Deports- Sources of Resources (Soil, Water, Forests and Biodiversity, Mineral Resources) Sinks or Waste Repositories-

Sources and Sinks

• Sources or Supply Deports- Sources of Resources (Soil, Water, Forests and Biodiversity, Mineral Resources)• Sinks or Waste Repositories- where we dump things. Pollution sinks (solid wastes and chemical pollutants).

Ecosystem Services: A Newly Defined Resource

• Public Goods that are not priced by the market economy.

• “Watershed Services”. Downstream residents pay upstream farmers to maintain forest- provides hydrological services.

• Paying farmers to grow trees for their carbon capture functions

• Pollination services from bees.

Soil Resources

• Soil a variable mix of inorganic and organic compounds, a “living layer” of the biosphere.

• 98% of human food produced in soil.

• Food and fiber crops cultivated on 12% of earth’ surface. 24 % is pasture. Rest is forests, deserts, mountains

Amazing Soil Facts!!

• An acre of good topsoil may house eleven tons of insects, worms, nematodes, fungi and microbes!

• The root system of a single four-month-old rye plant was found to have a surface area of 639 square meters, 130 times the surface area of the aboveground plant

• Surfaces of the particles in a single ounce of clay-rich soil-6 acres!

More Amazing Soil Facts

• Earthworm feces, known as castings-on a single hectare (2.7 acres) in a year, earthworms may deposit 500 metric tons of castings.

• To a great extent, the soil organisms do not just make the soil, they are the soil. Soil is almost a living thing itself.

• Now, what happens when you apply chemical fertilizers?

• Impact of chemical fertilizers on the soil-”going over the soils head, like feeding your children white bread”.

• “Petrochemicals feed its zombie productivity”

Pesticide Treadmill- In 1948 at the dawn of the chemical age, American farmers used 15 million pounds of insecticide and lost 7% of the crop to insects; today they use 125 million pounds and lose 13 percent.

Soil Erosion

Of earth’s present cropland• Soil eroding on from 16-38%.• In the US, Great Plains states have lost

half their topsoils.• Caused by overgrazing of livestock, poor

farming practices, and deforestation.• Effects-reduced soil depth, reduced water

absorption, and reduction in organic matter (Harper, p. 47)

Avoiding Erosion

• Terracing

• contour plowing

• multiple cropping (ground cover crops and corn-beans fix the nitrogen).

(Harper p. 86)

Water Resources

Water is a renewable resource, but

• If world’s water were 26 gallons, usable freshwater supplies for humans about one teaspoon.

• Very unevenly distributed over earth’s surface.

• Recharge rates of groundwater are very slow, about 1% a year.

Water Use and Waste

• People need 26.5 gallons a day (but in US 36 gallons in an average bath)

• 70% of water worldwide is for agriculture, but 70-80% of water in irrigation systems lost to evaporation or seeps into the ground.

• Industry is 23% of global water use. Takes 400,000 liters of water to make a car (50 million cars a year)

• Only 7-8% for domestic use (Harper p. 49)

Water Pollution• Contamination from agriculture: the countries that can

afford the most chemical inputs have the biggest problems: the US and Europe. Over 90% of Europe’s rivers have high nitrate concentrations.

• In developing countries, 90-95% of all domestic sewage and 75% of all industrial waste are discharged into surface waters without any treatment [sink]

• All of India’s 14 major rivers are badly polluted and ¾’s of China’s 50,000 kilometers of major rivers are unable to support fish.

water water microorganismsmicroorganisms

water insectswater insects

mosquito fishmosquito fish

bream (“brim”)bream (“brim”)

gargar

bassbass

alligatoralligator

HumansHumans

Mercury in the Everglades

• Remember the Mad Hatter from Alice in Wonderland ?

Irrigation a cornerstone of modern agriculture

• But much irrigation is “mining” the resource.

• Irrigation overdrafts lowered water tables by 20-30 meters in the Tamil Nadu region of India.

• Water tables in China declining by 1-4.5 meters a year.

• Ogallala Aquifer in Nebraska.

One quarter gone by 2020.

Drip Irrigation

•allows small quantities of water to trickle slowly into the soil over long periods.

• sprinkler systems waste a lot of water

• Drip systems use less water, because it is applied where the plants need it most - in the region of the root hairs.

• Irrigation efficiency improvements have helped stem the Ogallala aquifer’s depletion.

• Since it peaked in 1974, water use in the Texas high Plains has fallen by 43 percent.

• Annual average of Ogallala depletion has fallen from 2 billion cubic meters during the late 1960s to 241 million cubic meters in recent years

Deforestation

• Two-thirds of forests that once existed are gone (historical deforestation for agriculture).

• 12% of earth’s surface is boreal forests (Canada, Russia, Scandinavia)

• Temperate Zone forests tend to be stable or recovering.

• Most current losses in tropical forests.

Tropical Forest Biodiversity

• Tropical forests constitute only about 5% of the earths surface, but have 50% of all terrestrial species, 4-6,000 species lost a year in tropical forest.

• Economic value of forest-medicinal plants,

• Medicine Man with Sean Connery..

Initiatives to Preserve Forests

• Promoting Sustainable Use.• Debt for Nature Swaps• Preserving Nature in Place• Gene Banks and Repositories• Bioprospecting• International Treaties

(harper, page 63)