Agriculture Reference
In-Depth Information
The figures indicate that the benefits of tackling water pollution from agriculture
are potentially in excess of £300m per year and can be as high as over £600m
Attributing figures to the financial cost of the damage to the water environment from
agriculture is a difficult and complex process. It is not currently possible to disaggregate
the figure shown in Table 1 further to attribute proportions to individual pollutants.
A project currently funded by Defra is working to bring together as much information as
possible on the link between farm practices, impacts on water quality and the categories
of cost outlined in Table 1.
The environmental impacts of water pollution from agriculture
Over the last two decades, much effort has been put into cleaning up UK rivers and
lakes. Since 1990, over £20b has been spent upgrading the sewerage infrastructure in
England and Wales in order to improve the quality of discharges and hence the quality of
receiving water. Limit values control the amount of pollution that industries are allowed
to discharge in order to meet Environmental Quality Standards and controls have been put
in place to reduce or ban the use dangerous substances. All these improvements have lead
to a steady increase in the quality of our waters (for more details see http://defraweb).
For example, there have been significant improvements in drinking water quality every
year since 1997 (99.88% of the 2.97m drinking water test samples taken in England and
Wales in 2003 met stringent quality standards) as well as in bathing waters (around 98%
passing EU standards), and about 69% of rivers in England are now of good biological
quality. Despite significant improvements in the water quality of our rivers (mainly as a
result of a reduction in point-source pollution) there are still valuable improvements to be
made, particularly to the ecological health of our rivers and other waterbodies. The main
challenge we face is to address diffuse water pollution from agriculture — in the UK 60%
of the nitrogen load and 43% of the phosphorus load in surface waters come from
agriculture.
Excess levels of nutrients in water contribute to the process known as eutrophication,
which refers to the process of nutrient enrichment of either aquatic or terrestrial
ecosystems. The higher levels of nutrients stimulate plant growth, which can adversely
impact the productivity and biodiversity of ecosystems leading to excessive growth, or
"blooms", of algae, which causes oxygen depletion, making waters uninhabitable for fish
and other animal life. In freshwater systems, phosphorus as phosphate is considered the
main nutrient limiting the rate of plant growth while in coastal waters, nitrogen as nitrate
or ammonia is considered the limiting nutrient. The eutrophication of water and its
contamination by material with high biochemical oxygen demand (BOD), pesticides,
veterinary medicines and soil all impact on the aesthetic, recreational, conservation and
biodiversity value of water. Contamination by faecal microorganisms gives rise to human
and animal health risks (for more details see Defra 2004a).
Long-term monitoring records, export coefficient modelling and palaeolimnological
studies all indicate that nutrient concentrations in UK freshwaters are greatly enhanced
above natural levels and have had considerable ecological effects, particularly in the last
50 years.
There are large regional differences in the degree to which lakes and rivers deviate
from a 'natural/background' level in the UK, with less impacted sites predominating in
less agriculturally-intensive (and less populated) landscapes, particularly Cumbria and the
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