Predicting the Future: Lessons from the
Distant Past
A scientist in the US
Geological Survey
National
Ice Core
Lab. Ice cores, which
are samples taken
from polar ice caps
and mountain glaciers,
provide
clues
about changes in
Earth's climate and
atmosphere going
back thousands of
years.Our ability to predict future ecological impacts of climate change stems largely from what we
know about the past. Rocks, ice cores, cave formations, tree rings, sediments, and other natural
"climate recorders" have offered clues about how ecosystems respond to major climate shifts.
Earth has experienced a series of ice ages over the past million years. Around 21,000 years
ago—during the peak of the last ice age—most of Canada and the northern United States was
under thousands of feet of ice. Arctic vegetation thrived in Kentucky, and sea levels were about
400 feet lower than today. That ice age ended as subtle changes in the Earth's orbit slowly
warmed the globe. This and other periods of cooling and warming caused widespread ecological
changes: Some ecosystems shifted to locations
with more favorable conditions, others vanished,
and new types of ecosystems emerged.
Climate change in the coming decades could be
much more rapid on a sustained, global basis than
the transitions into and out of many past ice ages.
In past ice ages, ecosystems were pushed off large
swaths of Earth's surface as ice-dominated landscapes
advanced, but when the change was slow
enough—over many thousands of years—similar
ecosystems reassembled again as the ice retreated.
There have also been abrupt changes in the past,
but the rate of change in the current era is expected
to be both global and rapid. Ecosystems can be
particularly vulnerable when major climate changes
happen over a relatively shorter period of time.
One of the major concerns about the future is that climate changes may happen too fast to
allow many organisms to respond. Some individuals and species can adapt or move faster or
farther than others. For example, a long-lived tree species may take decades to shift to a new
range, while an insect species could shift its range much more quickly. Understanding how
quickly species and ecosystems can adjust is one of the key challenges in climate change
research.
Dealing With Uncertainty
Although we can glean clues about the likely
impacts of future climate change from recent
observations and research into Earth's past,
the picture is still incomplete and our predictions
are uncertain. Future climate change
will likely be fundamentally different from
changes Earth experienced in the past because
of the high temperatures that are projected,
the rate of climate change, and the fact that
climate change is occurring in a setting
where human actions have already altered
natural ecosystems in many other ways.
Despite uncertainties about what the future
holds, decisions can be made now. Strategies
for managing ecosystems in the future will
need to pay special attention to the issue
of uncertainty. It will be important to make
decisions based on the best currently available
information, and implement them in
a way that preserves the ability to make
adjustments in the future as more information
becomes available.
Human Causes, Human Solutions
Image © 2009 Jupiterimages
Corporation.Climate change is one of the defining issues of the 21st century. Decisions about climate
change over the coming decades will likely reverberate through centuries: it is generally
agreed that a change in such factors as carbon dioxide emission rates would
change the projected outcomes.
Humans are challenged to find a set of policies, practices, and
standards of behavior that provide long-term economic opportunities
and improved quality of life around the world
while maintaining a sustainable climate and viable ecosystems.
Recent analyses by U.S. and international
experts conclude that the world should invest in
minimizing the amount of climate change that
occurs and in adapting to the changes that cannot
be avoided. The appropriate level, financing,
and structure of these investments are
questions to be discussed among all members
of society.
Image © 2009 Jupiterimages Corporation.Some of the issues are so big that the
involvement of governments will be
required. These include decisions about
the best ways to reduce a country's carbon
emissions and where to invest funds
in research on alternative energy sources.
Other decisions are best addressed at the
individual, family, or business level. Each
time a car, home appliance, or lightbulb is
purchased, a decision is made that has a small
influence on climate change. But many small
decisions, made by billions of people, can combine
to have very large effects.
We know that climate change is not the only stress ecosystems
are facing. An important way for society to help reduce the ecological
impacts of climate change is by creating conditions that make it
easier for species in ecosystems to adapt—that is, by reducing other humaninfluenced
ecosystem stresses. Well-thought-out approaches to and investment in
conservation, sustainable agricultural practices, pollution reduction, and water management
can all help ecosystems withstand the impacts of a changing climate.
The climate challenge is large and complex. It is unlikely
that this challenge can be solved by using any single strategy
or by the people of any single country. But it is very
likely that the dedicated efforts of many people, working
hard from different angles and through diverse strategies,
can help address this important challenge and its ecological
consequences.
This web page is based on the National Academies' educational booklet
Ecological Impacts of Climate Change.
