Welcome to Planet Earth

SustainabilitySustainability

• In this course we will focus on one environmental resource important to human populations: WATERWATER

• When populations grow too large, they can exploit all resources in a region and are then forced to emigrate

• Can you picture a world in which there is no room or resources for human life?

Population Growth

• There are approximately 5.8 billion people in the world

• The global birth rate is about 27 births per 1000 people per year

• How many babies were born in the last 3 minutes?

• What additional information would you need to know to calculate the increase in world population over the past 3 minutes?

Projected population growthProjected population growth

Figure 1.12 on page 12

Why are there regional differences in population growth?

Where do most people live? Why?

Population density in the Mid- Atlantic Bight

Earth is always changingEarth is always changing

• Some changes happen on time scales we can observe: the tides rise and fall, the seasons change

• Other changes occur over long time periods and we must infer their presence: mountains are built and eroded, plants die and become fossil fuel

• Most resources on Earth are created much more slowly than we consume them

Geochemical CyclesGeochemical Cycles

• What is a cycle?

• Reservoirs in the water cycle

• Fluxes in the water cycle

• Box models

How do you know a How do you know a cycle when you see cycle when you see

one?one?

What are some What are some everyday examples of everyday examples of

cycles?cycles?

Dictionary definition of cycle:Dictionary definition of cycle:

Any period of time or complete process of growth or action that repeats itself in the same order

The basics of a geochemical cycleThe basics of a geochemical cycle

• Reservoirs - a place where the matter accumulates

• Fluxes – transfer of matter from one reservoir to another

• Residence time – the amount of time an average “piece” of matter (molecule, atom) resides in the reservoir.

Residence time is calculated:Residence time is calculated:

Amount of matter in reservoir

Removal rate (or supply rate)

Let’s create our own example!

Focusing on the hydrologic cycle

Major reservoirsMajor reservoirs

• Oceans 97.5%

• Glaciers 1.81%

• Surface water (lakes, streams) 0.016%

• Soil moisture 0.005%

• Atmosphere 0.001%* Nearly all of the water on earth is in the ocean and glaciers

Major fluxesMajor fluxes

• Condensation

• Precipitation

• Infiltration

• Run-off

• Evapotranspiration

We will define each of these today and then spend the next few weeks talking about each in detail.