Botkin Environmental Science Earth as Living Planet 8th txtbk

566 CHAPTER 24 Our Environmental Future
Table 24.1 GLOBAL THRESHOLDS THAT, TRANSGRESSED, COULD CAUSE UNACCEPTABLE
ENVIRONMENTAL CHANGE [FOR DISCUSSION PURPOSES ONLY; NOT TO BE TAKEN AS FACTS]
SYSTEM PARAMETER SUGGESTED PRESENT STATUS PRE-INDUSTRIAL
THRESHOLD
LEVEL
Human population Billions of people 5.0 6.8 1.0
Climate Carbon dioxide 350 390 280
concentration
(parts per million)
Biological Portion used by 0.6 1.2 100 0.1–1.0
loss (extinction)
(number of species per
million species per year)
Nitrogen use Amount removed from 35 120 0
the air for human use
(millions of tons per year)
Phosphorus use Quantity flowing into 11 9 -1.0
the ocean (millions of
tons per year)
Land transformation % of land converted 15 12 Low
to agriculture
Global freshwater use km 3 /yr 4,000 2,600 415
Air pollution Metric tons per year To be determined To be determined To be determined
Water pollution Metric tons per year To be determined To be determined To be determined
Source: Modified from J. Rockström et al., 2009. “A Safe Operating Space for Humanity,” Nature 461: 472–475. doi:10.1038/461472a.
SUMMARY
A fundamental question, continuously debated in a
democracy, is the extent to which human societies and
their environment can function as self-organizing systems,
and how much formal planning—laws and so
on—is necessary.
Both natural ecosystems and human societies are complex
systems. The big question is how the interaction
among these can lead to the long-term persistence of
both, and perhaps even improvements.
Mistakes are always likely; advance planning, including
rapid response, is essential to maintaining the best
environment.
Our environmental laws have grown out of a combination
of the English common law—derived from custom
and judgment, rather than legislation—and American
perspectives on freedom and planning.
In the 19th and 20th centuries, America experimented
with a variety of approaches to conserving
nature, some involving laws, some new kinds of plans
and organizations. The best combination is yet to be
determined.
International environmental law is proving useful in
addressing several important environmental problems,
including preservation of resources and pollution
abatement.
Global security, sustainability, and environment are
linked in complex ways. Solving environmental problems
will improve both sustainability and security.