5 May 2009 - Annual variations
in climate have considerable implications
for the aquatic environment. 2007 was a
record warm year as far as temperature is
concerned as well as being one of the wettest
years ever recorded. And the raised levels
of precipitation
could be read directly in the load in the
aquatic environment of the nutrients nitrogen
and phosphorous from wastewater treatment
works as well as agriculture.
Alone from wastewater
treatment works the discharge of nitrogen
and phosphorous to watercourses was approx.
20 per cent higher in 2007 than in the previous
year due to increased rainfall. The amount
of nutrient-rich water that passed through
the works was simply greater.Similarly,
the leaching ofnitrogen from agricultural
sources was also significantly greater.
Increased rainfall therefore increases the
addition of nutrients to the aquatic environment
and thereby the risk of algal blooms and
deoxygenation in lakes, fjords and in the
open sea. The risk of deoxygenation is enhanced
by higher temperatures, as water can hold
less oxygen at higher than lower temperatures.
The above is featured
in the annual reporting of monitoring of
the aquatic environment and nature under
the national monitoring programme NOVANA.
The results are presented in the report,
’Vandmiljø og Natur 2007’ (Aquatic
Environment and Nature), prepared (in Danish)
by Denmark ’s National Environmental Research
Institute (NERI), Aarhus University , in
collaboration with the Agency for Spatial
and Environmental Planning and the Geological
Survey of Denmark and Greenland (GEUS).
NOVANA is an integrated
programme of comprehensive and systematic
monitoring of nature and environment. The
monitoring addresses significant parts of
Denmark ’s international obligations as
well as national requirements with regard
to monitoring, e.g. demonstrating the effects
of various measures such as the plans for
the aquatic environment.
The monitoring programme
covers air, water, habitats on land, as
well as plant and animal species.
Main results in ’Vandmiljø
og Natur 2007’
The nutrients, nitrogen and phosphorous:
Overall there has been a considerable reduction
in additions of these nutrients to the aquatic
environment since initiation of the monitoring
programme for the plan for the aquatic environment
in 1989, but in recent years there have
been no clear signs of change. Annual variation
in the discharges from point sources and
agriculture has been large however due to
variations in rainfall.
Most pronounced is the
reduction in discharge from point sources
(wastewater treatment works, industry and
aquaculture) of organic material, nitrogen
and phosphorous. Evaluation of the Plan
for the Aquatic Environment II in 2003 concluded
for agricultural discharge of nitrogen that
the goal for reduction of leaching was attained.
The goal in the Plan for the Aquatic Environment
III was for leaching of nitrogen to be reduced
by a further 13 per cent in relation to
2003. In the mid-term evaluation of the
Plan for the Aquatic Environment III in
2008 it was not possible to demonstrate
a significant fall in nitrogen leaching
from 2003 to 2007.
The phosphorous balance
in agriculture (i.e. the difference between
the amount of phosphorous applied and that
harvested) has fallen by 68 per cent during
the period 11000-2007. In the mid-term evaluation
of the Plan for the Aquatic Environment
III it was assessed that the interim goal
of a 25 per cent reduction in the phosphorous
balance by 2009 can be attained. Attainment
of the goal for reduction of the phosphorous
load by means of construction of approx.
50,000 ha buffer zones along watercourses
and lakes is evaluated in the mid-term evaluation
of the Plan for the Aquatic Environment
III to be a long way off.
Nitrogen and phosphorous
concentrations in lakes, fjords and marine
areas have declined over time as a result
of changes in the loads of these nutrients.
This fall in nutrient additions has improved
environmental conditions in lakes, whilst
biological conditions in marine areas have
not improved.
As far as watercourses
are concerned, during the period 1994-2007
a distinct improvement took place in biological
conditions measured based on fauna. In addition
to improvements in wastewater treatment,
this trend is due to improvements in physical
conditions, e.g. resulting from changed
practices in the maintenance of watercourses.
Groundwater: The frequency
with which pesticide traces have been detected
in groundwater monitoring was in 2007 just
over 35 per cent, which is the same level
as in the last 3-4 years and slightly higher
than in the year before. This is attributed
to that, since 2004, pesticides have been
investigated exclusively in groundwater
created after c. 1950. Also, since 2004,
an additional herbicide, metribuzin, has
been investigated which up until 2003 was
used in potato fields.
Environmentally harmful
substances: In the fjord and marine environment
measurements of heavy metals and organic
substances in mussels now permit description
of statistically significant trends. For
heavy metal concentrations both upward and
downward trends are evident, while for organic
substances a downward trend is displayed
in all cases. Measurements of tributyltin
(TBT), used up until 2003 as an antifouling
agent for the hulls of ships and boats,
showed a significant fall at approx. one
quarter of the measuring stations investigated.
Concentrations however continued in the
majority of cases to be, in 2007, above
those equivalent to significantly (‘markant’)
polluted and in several cases over the concentration
equivalent to very heavily (‘meget stærkt’)
polluted.
Terrestrial habitats:
The monitoring programme started in 2004;
therefore data is not yet sufficient to
assess trends in habitat structure and function.
In this year’s report analysis has therefore
been made of the most suitable indicators
for structure and function. The analysis
shows that indicators of nutrient levels,
excess growth and hydrology are among the
best suited, but this can differ from one
habitat type to another. Even though the
habitat monitoring only includes four years’
data, in a few cases it has been possible
to identify statistically significant trends
– for example, dry calcareous grassland
and dry acid grassland, where a rise in
the number of nutrient-loving species is
evident, and grey/green dunes, where in
the period 2004-2007 increasing occurrence
of the invasive species, Rosa rugosa, has
been recorded.
Species: For the 50
species described in the report the picture
is mixed. Some species are assessed to be
of favourable conservation status (e.g.
green snaketail), others not so (e.g. Graphoderus
bilineatus), and others again to be of unknown
status (e.g. species of whorl snail).
For a number of species
it is possible to assess trends in population
size, including the birds which are monitored.
The general picture for the breeding birds
monitored is that populations lie below
the proposed scientific criteria for favourable
conservation status (e.g. tern or tawny
pipit), while the majority of the waterbirds
monitored lie above the criteria (e.g. oyster
catcher and curlew).
Poul Nordemann Jensen
