Biology 12

Chapter 13 Ecological Principles • MHR 455

The Impact of Humans on

Biogeochemical Cycles:

A First Look

Could the destruction of the Easter Island
ecosystem have been due to the upset of one or
more biogeochemical cycles? Can humans actually
have a large enough impact to disrupt natural
cycles? These questions will be examined in more
detail in Chapter 15; for now, you need only look at
some general aspects.
All over the world, researchers have realized
that because of weather variations, the rates of
biogeochemical cycling and the routes taken by
nutrient molecules differ from time to time, even
within the same ecosystem. As a result, it is
necessary to study ecosystems for long periods of
time to fully understand the movement of nutrients
and the time required to complete certain cycles or
parts of cycles. Many scientists are therefore
conducting what is often referred to as long-term
ecological research (LTER), either by monitoring
change in certain variables over a broad area or by
studying specific ecosystems in detail.

One very productive LTER project has been in

existence since 1963 at the Hubbard Brook

Experimental Forest in New Hampshire (see

Figure 13.30A on the following page). At this

location, scientists began by monitoring the amount

of important nutrients that entered the ecosystem

(contained in rain and snow) and the amount that

left it (flowing out in streams or being given off to

the atmosphere by plants). The results indicated

that the amounts were almost balanced — cycles

operating within the forest ecosystem conserved

the nutrients the ecosystem contained.

http://www.mcgrawhill.ca/links/biology12

In some cases, LTER involves members of the public assisting

in the collection of data that are later analyzed by scientists. In

Canada (as well as elsewhere in North America), programs like

Frogwatch, Feeder Watch, Tree Watch, The Breeding Bird

Survey, and The Christmas Bird Count encourage the

participation of individuals and groups. Various web sites show

you how to get involved, obtain data, analyze populations, or

learn more about various LTER projects. To get started, go to

the web site above, and click on Web Links.

WEB LINK

decomposers

animals

plants

rain

geological uplifting

weathering of phosphate from rocks

run-off

phosphate in solution

chemical precipitation

detritus settling to bottom

sedimentation = new rocks

leaching

phosphate in soil

Figure 13.29Manufacturers have responded to the
demands of various environmental groups and removed
most of the phosphates from laundry and dishwashing

detergents. Why do you think these groups campaigned for

the removal of phosphates?