A perennial problem with ecology is that it is a discipline that is far better at describing problems than it is at solving them. The Water Framework Directive (WFD) encapsulates this: after nineteen years, we have a pretty good idea of the condition of Europe’s waters but have made very little progress in restoring the half that do not yet achieve good ecological status.
The reason for this is, I suspect, because describing the problem is a task that lies squarely within the remit of a scientist whilst finding solutions requires interactions that go beyond the boundaries of science, encountering vested interests along the way. The agricultural sector’s enthusiasm for the environment is tempered by their desire to maximise yield and earn a living from the land, politicians are wary of regulations that may deter business or raise prices for the consumer and all of us are too wedded to the luxuries that the modern world offers.
The WFD can be seen as an embodiment of the social contract, articulated by philosophers such as Thomas Hobbes whereby individuals forego some rights in order to transcend the state of nature (“… nasty, brutish and short.”) and give us access to the benefits of an ordered society. In this case, we all consent to forego some freedoms in return for a share in the benefits that a healthy aquatic environment will bring to all of us. “Freedom” might seem like a weighty word in this context but anyone who has watched their sewerage charges creep steadily upwards over the past twenty years should recognise this as the price we pay for the freedom to flush away life’s less desirable by-products.
The problem is defining the point at which we hand over our natural rights to a higher authority. We understand this when driving: an urban speed limit of 30 miles per hour reflects the point at which the risk we pose to other road users are deemed societally unacceptable and our right to drive as fast as we wish has to be curtailed. If we can translate that principle into environmental governance then we can set “speed limits” for the major pressures that impact on the aquatic environment. How do we get from an ecologist’s understanding of a “healthy” river (“good ecological status”, in WFD parlance) to the “speed limit” for nutrients, widely recognised as one of the major pressures affecting both freshwater and marine systems?
That’s been the focus of some work I’ve been doing under the auspices of the European Commission’s Joint Research Centre, one strand of which has just been published in Science of the Total Environment. This paper looked at the threshold concentrations for nutrients (phosphorus and nitrogen) used by EU countries, noting the very wide range of values chosen as the national “speed limit”. The situation is complicated because, just as is the case for roads, different types of rivers require different limits and we had to look for variation between countries amidst an array of variation within countries. What emerged, however, was a clear relationship between the threshold values and the method used to set the standard. Those that had applied statistical or modelling techniques to national data generally had tighter thresholds than those that relied upon “expert judgement”. I’ve included the two figures from this paper that make this point.
Range of good/moderate lake phosphorus (a) and nitrogen (b) threshold values grouped by method used to determine the value. Different letters indicate groups that are statistically different (p ≤ 0.05). Fig. 7 from Poikane et al. (2019).
“Expert judgement” is one of those slippery terms that often creeps into official reports. There needs to be space within a decision-making process for an experienced professional to see through the limitations of available evidence and present a reasoned alternative. However, “expert judgement” too often becomes a shorthand for cutting corners and, in this case, grabbing numbers from the published literature that seem vaguely plausible. There is also a darker side because, having unhitched decision-making from the evidence, “expert judgement” can become a euphemism for the “art of the possible”. I have seen this occur during discussions around setting and revising river phosphorus standards in the UK: the regulators themselves are under pressure to balance environmental protection with economic development and tight standards can potentially limit what can be done in a catchment.
Another of our recent papers (this one’s not open-access, I’m afraid) shows that setting standards using empirical models is far from straightforward and we also recognise that standard setting is just one part of a longer process of nutrient management. However, setting inappropriate standards simply as an expedience seems completely barmy, as you are never going to attain your desired ecological benefits. The cynical view might be that, as the process of environmental change is invariably greater than the electoral cycle, there is limited accountability associated with such decisions, compared with more immediate political capital kudos from bringing investment and jobs to a region.
Range of good/moderate river phosphorus (a) and nitrogen (b) threshold values grouped method used to determine the value. Different letters indicate groups that are statistically different (p ≤ 0.05). Fig. 8 from Poikane et al. (2019).
All of our work has shown that, in most cases, the relationship between biology and nutrients is weak and, for this reason, large datasets are needed if robust inferences are to be drawn. This leads to one further consequence of our work: setting environmental standards may only be possible if countries pool their data in order to produce big enough datasets with which to work. This is particularly the case for smaller countries within the EU, but also applies to water body types that may be relatively infrequent in one country but are more widespread elsewhere. I had recent experience of this when working on the Romanian stretches of the Danube: they simply did not have a wide enough gradient of conditions in their own territory, and we had to incorporate their data into a larger dataset in order to see the big picture (see “Beyond the Tower of Babel …”). Writing about the benefits of international collaboration as the Brexit deadline looms obviously has a certain irony, but it needs to be said. Far from being the distant and unaccountable law maker of Brexiteer mythology, in this field the European Commission has been quietly encouraging Member States to share experience and promote best practice. One can only speculate about the future of the UK environment once free of Brussels oversight.
Philips, G., Teixeira, H., Poikane, S., Salas, F. & Kelly, M.G. (2019). Establishing nutrient thresholds in the face of uncertainty and multiple stressors: a comparison of approaches using simulated data sets. Science of the Total Environment684: 425-433.
Poikane, S., Kelly, M.G., Salas Herrero, F., Pitt, J.-A., Jarvie, H.P., Claussen, U., Leujak, W., Solheim, A.L., Teixera, H. & Phillips, G. (2019). Nutrient criteria for surface waters under the European Water Framework Directive: Current state-of-the-art, challenges and future outlook. Science of the Total Environment 695.
Note on figures:
The methods used by Member States to derive nutrient thresholds are described in more detail in Poikane et al. (2019). In brief, the approaches are:
1 – regression between nutrient and biological response;
2 – modelling;
3 – distribution of nutrient concentrations in water bodies classified (using ecological criteria) as high, good or moderate status;
4 – distribution of nutrient concentrations in all water bodies using an arbitrary percentile;
5 – expert judgement. This includes values taken from the literature or from older European Directives. For example, for nitrate, the common use of the value 5.65 mg-N L−1 in freshwaters is likely to be derived from the guideline value of 25 mg L−1 of nitrate in the Nitrates Directive (91/676/EEC) or now repealed Drinking Water Directive (80/778/EC).
6 – The so-called OSPAR Comprehensive Procedure is used widely in coastal and transitional waters. In this, a water body is considered to be an ‘Eutrophication Problem Area’ if actual status deviates 50% or more from reference conditions.
7 – insufficient information.