But how should we deal with them? The more notorious environmental villains
such as DDT, PCBs and plutonium are so toxic that zero emission of such
substances is a clear and feasible policy objective. Nitrates, by contrast, are
essential for the normal functioning of a healthy ecosystem. Only when present
in excess can they be considered pollutants. Deciding whether levels at a
particular site lie within expected, natural variation or are dangerously high,
is a subtle and demanding task. It makes a simple “seek and destroy” approach
impossible. And once the need for action has been decided, there is the
political task of tackling the diffuse inputs of nitrates from agricultural
fertilisers, slurry run-off, sewage, atmospheric deposition and other
sources.

Despite these problems, many governments are now dealing with nitrates. Some
US states have brought in integrated management programmes to control the way
that fertilisers—one of the prime sources—are applied. Countries
that belong to the European Union are bound by a directive designed to protect
public and environmental health by identifying “nitrate vulnerable zones” (NVZs)
in which nitrates have reached such dangerous concentrations that plans must be
developed to reduce inputs. Where public drinking water is affected, the
directive demands that action be taken if nitrates exceed 50 milligrams per
litre—the level deemed to be dangerous to human health. But what of other
areas?

EU member states are also required to take action if nitrates appear to be
causing damage to ecosystems. Environmentalists, scientists and farmers around
Europe have had to wait years to see how their governments interpret the
legislation. The Netherlands, Sweden and Denmark have all adopted a safety-first
approach. Recognising the difficulties of searching for case-by-case evidence,
they are establishing nationwide action programmes designed to prevent
discrimination against any particular groups of farmers.

Other EU countries, including Britain, have chosen a different road. Only
sites where evidence of ecological damage is clear are designated NVZs. On this
basis none has yet been declared in Britain.

Where better to set such a precedent than the country’s most intensively
studied estuary? The Ythan, a nationally important nature reserve some 20
kilometres north of Aberdeen on Scotland’s east coast, is the leading contender
for designation. Forty years of data show rising nitrogen concentrations in the
water. Huge mats of algae now coat the mud flats in summer, displacing wading
birds and killing many of the invertebrates that underpin the food chain. This
has convinced the Scottish Environment Protection Agency, along with scientists
working on the site, that the estuary is polluted.

But sceptics point out that nothing is certain. No one can prove beyond all
doubt that the algae have grown because of the nitrogen. Perhaps the algae was
always there, but has only been recorded recently? Maybe it spread because of a
change in climate or tidal patterns?

Even the best scientific assessments will always leave room for such doubts.
Which is why environmentalists call for a precautionary approach—giving
the environment the benefit of the doubt in cases of scientific uncertainty.
Because nitrates are a natural part of the ecosystem, this cannot mean
“eliminate the suspect at source”. Instead it implies that action should be
taken as soon as the balance of probabilities implicates nitrates, rather than
waiting for proof beyond reasonable doubt.

The last government refused to designate the Ythan because there was no
“incontrovertible proof”. Its successor, elected in 1997, signed Britain up to
international agreements that enshrine the precautionary principle. This makes
its stance over nitrates particularly puzzling. Last September it refused NVZ
status to the Ythan because the evidence of nitrate pollution is “not
conclusive”. This just won’t wash. Complex pollution cases can never be decided
conclusively. It’s time to stop using uncertainty as an excuse for inaction on
nitrates.

Shell has consistently maintained that its preferred option of disposal in
the deep sea represented the best scientific solution. But as Shell itself said
in its report (Brent Spar, Shell, 1995): “An emotive Greenpeace
campaign gave it a symbolic significance beyond any rational, scientific
calculation of its impact.” With a few notable exceptions, such as New
żěè¶ĚĘÓƵ (Editorial, 1 July 1995, p 3), most scientists commenting since
the event have agreed. The journal Marine Pollution Bulletin stated: “A rational
balancing of the expected environmental effects favours deep sea disposal” (vol
30, p 578). An editorial in Nature (vol 375, p 708) was even stronger:
“Shell Oil’s decision not to sink a used oilrig at sea is a needless dereliction
of rationality.” It claimed that the whole issue had “again exposed the
shallowness of Greenpeace’s arguments on scientific issues”.

The environmentalists’ concerns addressed two distinct areas. First, there
were the immediate effects of sea disposal. Sociologist Brian Wynne has called
these “first-order risks”—impacts measurable and describable by science
(Global Environmental Change, June 1992, p 111). Then come the wider
social implications, or “second-order risks”. Would Brent Spar set a precedent
for other structures and substances? Can we trust a case-by-case approach to
prevent cumulative damage? Such questions reach beyond science.

There is now almost universal agreement on the first point. A Shell spokesman
told me: “What is clear is that the environmental impact would have been minute
. . . I haven’t come across a single scientist who would disagree with that.”
Greenpeace concedes this point: “There would have been some immediate but
localised environmental impact,” one of its employees told me. “I don’t think
there would have been any immediate impact on human health from a single
installation, but that was never the point.”

So what exactly was the point? I suspect it was all about second-order risks,
and precedent in particular. Relevant law begins with rare clarity, with the
1958 Geneva Convention on the Continental Shelf, which states that all rigs must
be removed. But things quickly get hazy. Exceptions may be allowed for “bulky
wastes”. Sea dumping should only happen after the licensing authority has “had
regard” to the availability of alternative methods. Naturally occurring
radioactive material (such as that on the platform) might, or might not, be
subject to the international moratorium covering sea disposal. Where legal
phrases are so plastic, lawyers look for the hard mould of case history to firm
them up. So it seems fair to suppose that the Brent Spar would indeed have acted
as a precedent, at least for structures of a similar kind.

Does this matter? Some scientists argue that the deep oceans are an
excellent place for all sorts of waste. In the words of a correspondent to
Nature (vol 376, p 208): “As a result of the misguided lobbying of
emotional environmentalists such as Greenpeace, the use of the oceans as a waste
depository has been denied to applied scientists competent to take
»ĺ±đł¦ľ±˛őľ±´Ç˛Ô˛ő.”

Buried in this statement are social assumptions that the environmentalist
perspective challenges: the notion of a “throwaway society” is one, and the idea
that risks should be adjudicated by small groups of experts is another. In its
report on the affair in 1996, Britain’s Natural Environment Research Council
reflected that disposal at sea involved social, economic, ethical and aesthetic
considerations that might be more important than any technical risk
assessments.

When Greenpeace squared up to Shell, it reminded us of the need for
a debate about waste which goes well beyond the first-order, “scientific”
uncertainties scrutinised in a case-by-case system. There’s nothing irrational
about that.