1. Thresholds of Environmental Sustainability :
The Case of Nutrients
Elisabeth Lipiatou
EUROPEAN COMMISSION, DG Research
Environment and Sustainable Development Programme
Policy aspects Unit

2. The workshop of November 6, 2001 in Brussels was a first attempt by the Environment of Sustainable Development Programme-/ Policy aspects unit of the EC Directorate General for Research to focus expertise towards defining and operationalizing the notion of “threshold”, especially as applied to nutrient over-enrichment in soils, and inland and marine waters. Context : EC Communication “A Sustainable Europe for a Better World: A European Union Strategy for Sustainable Development”.

3. In ecology, the non-reversibility could be studied through the notion of “Threshold”.

4. Thresholds :  carrying capacity for pollutants.  minimal population
Thresholds :  carrying capacity for pollutants  minimal population  maximum quantity of available resource  toxicity for human health The thresholds could translate into indicators for quality of different media or concentrations in the environment.

5. HUMAN ACTIVITY. ECOSYSTEM FUNCTIONNING
HUMAN ACTIVITY ECOSYSTEM FUNCTIONNING THRESHOLDS OF SUSTAINABILITY Policy TARGETS (e.g. % of reduction)

6. A process irreversible in the human time scale until some centuries could be reversible in the geological time scale of several million years.

7. Knowing there is a threshold is less difficult than quantifying the threshold and to use it in policy making. For this last purpose, it is also necessary to make an economic assessment in order to know, for example, the costs of the damages against the cost of avoiding the threshold (elements of a cost-benefit analysis).

8. We chose to focus on the important environmental problem of nutrient over-enrichment in soils, and inland and marine waters, and associated thresholds. Agricultural runoff, waste discharges and atmospheric deposition are the main source of nutrients in the marine environment. Nutrients are suspected to be behind the unexpected appearance in several coastal waters of toxic phytoplankton, which can kill fish, seabirds and mammals and which represent an emerging threat to public health and to the local/regional economies.

9. 1st Workshop on Thresholds of Environmental Sustainability : The Case of Nutrients November 6, nd Workshop on Thresholds of Environmenal Sustainability : The Case of Nutrients June 18, 2002

10. Question 1: Is there some general agreement as to what constitutes a “ threshold ”? Question 2: How could / should a critical threshold be used for nutrient policy formulation for the aquatic / marine environment?

11. Question 1 : The definition most close to consensus was that the notion of threshold is connected to the potential negative effects on the ecosystem through the concept of carrying capacity, which reflects the tolerance, and maximum performance of the ecosystem receiving the nutrient input. A nutrient threshold is also associated to eco-regions representing a complex factorial matrix. What do we mean by “nutrient” thresholds ? The conclusion was that we mean the sum of organic and inorganic nitrogen and phosphorus and carbon and silicon.

12. Increased co-operation between the various fields of natural and social sciences, combined with economics will be required in order to be able to estimate thresholds for nutrients including cost-benefit analysis.

13. Question 2 : Several case studies brought forward examples where adverse effects resulted from excess nutrient loading of coastal marine waters (Adriatic Sea, the Baltic Sea, and the inland Seto Sea, Japan). In all cases, the lack of adequate long term data series of nutrient measurements was identified as one of the main factors limiting the possibility to define the presumably exceeded nutrient thresholds. In addition to this, it was realised from the Q1 that attempts to establish nutrient thresholds would also have to include socio-economic factors such as cost benefit assessments.

14. Q2 : It was generally agreed among the discussants that established nutrient thresholds are needed as potentially important tools for communication between scientists, policy makers and the public. Furthermore, the need for more focused communication along these lines will increase as more attempts are made to work towards sustainable development.

15. Q2 : The group accepted that scientists should begin to explore the possibilities for producing estimates of nutrient thresholds from examples of marine systems, based on available data. Even though these may be inadequate, they could be an important way to break the present "deadlock" where scientists have partially identified serious environmental problems of excess nutrients, without yet providing focused arguments that may help policy makers and the public to take appropriate actions to address this issue.

16. Such estimated thresholds would serve in a similar role as models, by helping identify areas where more information is needed, while in the meantime best- available-case information is provided on which to build management policies.

17. Preliminary threshold levels based on a combination of data and judgement will inevitably promote further discussion, and will certainly generate strong opinions within the scientific community concerning the levels established for these nutrient thresholds for different water bodies.

18. Conclusions  Not surprisingly, this first exchange of ideas concerning nutrient thresholds generated broad impressions as to the complexities involved rather than solid recommendations. Nevertheless, these first considerations offer some suggestions as to the current understanding of this concept, and what needs to be done to improve the existing situation.

19.  Estimating the values of nutrient thresholds for ecosystems potentially threatened by future human impacts is therefore one of the critical challenges facing environmental sciences. Social and economic optima should be considered together with environmental parameters for the reduction of nutrients (cost-benefit and cost-effective analyses).

20.  The concept of nutrient thresholds is crucial in understanding the ultimate limits of human impacts on aquatic ecosystems, if sustainable growth of human populations is to be achieved.

21.  The existence of such thresholds is most easily realised from case histories such as those considered here, in which ecosystems were adversely affected by past cultural eutrophication ; and, with the clear implication that amounts of available nutrients had been exceeded beyond limits regulating acceptable development.

22.  Future work should be invested in an initial attempt to produce such estimates, even though they will lack scientific precision. They will serve a similar function to models, i.e., help identify areas where more information is needed, while in the meantime providing best- available case information on which to build management policies.

23.  Past experience suggests that society may pay dearly for development policies lacking such input, both in terms of actual economic loss through declining fisheries, etc., and by the more difficult to define loss to their living environment felt by human societies exceeding the limits to sustainable growth *****