Environmental Engineering Reference
In-Depth Information
sources. Apart from cement industries, power
supply of all the industries is based on the
burning of fossil fuels.
The carbon dioxide produced from industrial
units and urban sectors has differential effect on
coastal vegetation, and many of these reports are
contradictory. There are some evidences that
elevated carbon dioxide stimulates plant growth
at least in agricultural plant species (Kimball
1983
; Cure and Acock
1986
) where most of the
experiments have been carried out with green-
house grown plants. Eames and Jarvis (
1989
), in
an extensive review, reported some enhancement
of growth in juvenile trees and Drake (
1992
)
reported a signi
interactions between several different physio-
logical and environmental factors. Information is
needed from long-term assessments of growth
where high carbon dioxide concentration, tem-
perature, water stress and nutrient stress are
controlled.
Anthropogenic aerosols, particularly sulphate
aerosols from fossil fuel combustion, exert a
cooling in
uence. This, together with natural
variability, is believed to account for the relative
'
fl
in the graph of twentieth-century tem-
peratures in the middle of the century. The effect
of temperature fall has not been studied critically
for coastal vegetation. Researchers observed that
the optimum leaf temperatures for photosynthesis
in mangroves appear to be 28
plateau
'
cant impact of enhanced atmo-
spheric carbon dioxide on a wetland community
of sedge and grasses. Though there is evidence
that carbon dioxide enrichment will enhance
growth in seedling tree species, there is no
equivalent evidence that there will be long-term
forest growth in response to rising atmospheric
carbon dioxide. A growth response to carbon
dioxide may be manifest in belowground pro-
cesses of forest ecosystems which tend to be
nutrient and water limited. At the whole plant
level, carbon isotope composition data indicate
species variation in regulation of water loss with
respect to carbon gain. The limited data suggest
that not all species will respond similarly in
response to elevated atmospheric carbon dioxide
levels. In the case of mangroves, Ball and
Farquahar (
1984a
,
b
) reported that for
C and pho-
tosynthetic capacity falls to close to zero at leaf
temperatures of 38
32
°
-
C (Clough et al.
1982
;
Andrews et al.
1984
). It is generally accepted that
plant development will be accelerated by
increased temperature, as long as the temperature
reached does not exceed an upper threshold.
Very little is known about the effect of tem-
perature fall on metabolic processes in man-
groves and hence the authors are presently not in
a position to conclude the cooling effect caused
by anthropogenic aerosols on seaweeds, sea-
grass, salt marsh grass, etc. It has been reported
that algae can thrive well in cold environments.
Most of the primary productivity of Antarctica
involves free-living algae in lakes, and algal
symbioses with fungi (lichens, and the green alga
Prasiola
40
°
-
Aegiceras
corniculatum
the rate of
photosynthesis was limited by stomatal conduc-
tance to carbon dioxide and the internal ef
and
Avicennia marina,
sp.) and, as free-living cyanobacteria,
on land. In the surrounding oceans, phytoplank-
ton and sea-ice algae, as well as very large sub-
tidal macroalgae, especially those of the brown
algal order Desmarestiales, with kelp (
-
ciency of carboxylation involving the enzyme
RuBp carboxylase. These results suggest that for
these mangroves, photosynthesis would be
enhanced if the ambient carbon dioxide levels
were increased. Contrary to these results,
Cheeseman et al. (
1991
) after working on
Laminar-
iales
)
—
like organisms such as
Himanthothallus
granfdifolius
(with blades up to 10 m long and
1 m wide)
are found in plenty (Luning
1990
;
Fogg
1998
; Boyd et al.
2000
; Brierley and
Thomas
2002
; Thomas and Dieckmann
2002a
,
b
;
Wiencke and Clayton
2002
).
B. Modi
—
Bru-
guiera parviora
,
Bruguiera gymnorrhiza
and
Rhizophora apiculata
suggested that the photo-
synthetic performance was unlikely to be
enhanced by increased levels of ambient carbon
dioxide. The effect of carbon dioxide enrichment
on mangrove forests cannot be interpreted within
a simple framework as it will depend on complex
cation of Land Use Pattern
Prior to widespread fossil fuel use, humanity
'
s
largest effect on local climate is likely to have
resulted from alteration in land use pattern. Irriga-
tion, deforestation and agriculture fundamentally
