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Ecological Change and the Challenges
for Monitoring 1
Thomas Brydges 2
Abstract-Anthropogenic activities are changing the chemical
composition of the global atmosphere, as shown by the increasing
concentrations ofcarbon dioxide, methane, nitrous oxide and HFC's.
In addition, sulphur and nitrogen compounds have. changed the
chemical character of precipitation on a regional scale in North
America, Europe, and Asia. These changes in turn, alter the physical
properties of the atmosphere with responses such as stratospheric
ozone depletion, ground level ozone formation and modifications to
the radiation balance. Changes in radiation balance are expected to
increase the average global temperature. However, local and regional
changes in temperatures will be larger and more varied with areas,
such as Eastern Canada, having experienced a cooling trend.
(Environment Canada 1995)
The biosphere is affected by the chemistry and physics of the
atmosphere, so we would expect it to respond to these new conditions,
and it already has.
Emissions of sulphur dioxide and nitrogen oxides have altered
the chemical characteristics of precipitation in areas near and
downwind oflarge sources. Damage to lakes, forests, human health,
building materials and atmospheric visibility has been documented
in eastern North America. (Environment Canada 1997) That report
also drew attention to the fact that present control programs are not
strict enough to fully protect the environment. Further reductions
in emissions, particularly of sulphur dioxide, are needed.
Keeling et a11996, have reported on changes in the global carbon
cycle. The amplitude of the yearly cycle has increased by 20% at the
Mauna Loa, Hawaii observatory over the past 30 years and by about
40% over Arctic sites at Alert in Canada and Pt. Barrow in the
United States. In addition, the yearly minimum atmospheric
concentration in July is now observed to occur about a week earlier
than 30 years ago. These changes appear to be a response to
increasing average temperatures. Keeling et aI, ibid, noted "These
striking increases over 30 years could represent unprecedented
changes in the terrestrial biosphere, particularly in response to
some of the highest global annual average temperature since the
beginning of modern records, and particularly in response to plant
growth being stimulated by the highest concentrations of atmospheric
C02 in the past 150,000 years.
Briffa et al 1998 reported on tree growth from 300 locations at
high latitudes in the Northern Hemisphere. Over the past 50 years,
the expected patterns of growth related to temperature have not
been observed. Instead, growth rates are less than expected. While
Ipaper presented at the North American Science Symposium: Toward a
Unified Framework for Inventorying and Monitoring Forest Ecosystem
Resources, Guadalajara, Mexico, November 1-6,1998.
2Thomas Brydges, Environment Canada, Ecological Monitoring Coordinating Office, 867 Lakeshore Road, P.O. Box 5050, Burlington (Ontario),
Canada L7R 4A6. (Retired)
10
the reasons for these observed changes are not known, they are an
indication of wide scale disruptions of normal processes in the
boisphere. Such changes should be viewed at least as an early
warning of further responses to the changing atmosphere.
Alterations in atmospheric characteristics are taking on a more
complex pattern. The IPCC 1994, reported on interactions between
the global warming effects of greenhouse gases such as carbon
dioxide, methane, nitrous oxide and halocarbons and the cooling
effects of sulphur dioxide and stratospheric ozone depletion. The net
change in radiative forcing and corresponding global temperature
increase are difficult to defme precisely and the net global effect may
mask larger regional changes in temperature. There may also be
important changes in precipitation at the regional leveL
More recently, Wardle 1997, has reported on stratospheric ozone
depletion over Canada's Arctic. Low values of ozone in the spring
have been increasing in both frequency and severity, due to low
temperatures in the stratosphere. The lower temperatures in the
stratosphere may in turn be caused by higher concentrations of
carbon dioxide. He postulates that increasing atmospheric
concentrations of carbon dioxide will cause even lower temperatures
to occur in the winter stratosphere, thus increasing the ozone
depletion. This may happen even though the concentrations of
CFC's in the atmosphere have increased very little in past few years.
Overall, we can anticipate a wide range of complex ecological
responses to the changing atmospheric properties. The natural
resources that are being affected are the basis of large parts of the
economies of North America. It is essential that we record and
understand changes in these ecosystems in order to manage the
associated industries in a sustainable way. This represents a major
challenge for our monitoring programs, and particularly for the
integrated monitoring sites.
References ----------------------------------A State of the Environment Report, 1995. The State of Canada's
Climate: Monitoring Variability and Change. SOE Report No 951, Environment Canada.
Briffa, K.R., F.H.Schweingruber, P.D.Jones, T.J.Osborn,
S.G.Shiyatov & E.A.Vaganov 1998. Reduced sensitivity of recent
tree-growth to temperature at high northern latitudes. Nature
Vol 391, 12 February.
Environment Canada, 1997. 1997 Canadian Acid Rain Assessment,
Volume One, Summary of Results.
IPPC, 1994. Radiation Forcing of Climate Change. The 1994 Report
of the Scientific Assessment Working Group ofIPCC, Summary
for Policy Makers. WMOIUNEP.
Keeling, C.D., J.F.S.Chin & T.P.Whorf 1996. Increased activity of
northern vegetation inferred from atmospheric C02
measurements. Nature, Vol 382, 11 July.
Wardle D.1. 1997. Trends in Ozone over Canada, Ozone Depleting
Substances and the UV-B. Air Waste Management Association,
Calgary, 19 September.
USDA Forest Service Proceedings RMRS-P-12. 1999