Several factors need to be kept in mind when choosing indicators (and, where appropriate, targets) for SEA:
- should they be input or outcome indicators/targets?
- should social and economic indicators/targets be included?
State, pressure, response; input, outcome
Indicators and targets can be divided into three types:
- state indicators that describe the state of the environment, for instance ambient NOx levels;
- pressure indicators that describe human pressures on the environment, for instance emissions of NOx; and
- response indicators that describe responses to these pressures, for instance 'Percentage of cars with catalytic converters' or 'bus frequency on route X'.
A range of organisations, notably the OECD, use these distinctions when describing their indicators.
The distinctions between state, pressure and response indicators are not always so clear in practice, particularly for social and economic issues. However they illustrate an important concept in SEA: the distinction between inputs and outcomes.
Outcomes are end-states, for instance 'clean air' or 'healthy people'. Inputs are the things that authorities do to try to achieve desired outcomes, for instance 'pedestrianisation of the city centre' or 'provision of more playing fields'. Inputs are means by which outcomes are reached. Outcomes = state, input = response.
An easy way of distinguishing between input and outcome is by asking "why is this being proposed?" until no more answer can be found:
Q: Why are you proposing a new power station?
A: To produce more electricity.
Q: Why do you need to produce more electricity?
A: To heat houses.
Q: Why do you need to heat houses?
A: To keep people healthy.
Q: Why do you need to keep people healthy?
... (keeping people healthy is the outcome; all the others are inputs)
Whether input or outcome indicators are used in SEA may well be important , as shown in the figure below.
Below are two scenarios. In each case, the city planners could present information on NOx ambient levels (state) or bus frequency. Which indicator should they use in each case?
For both scenarios, ambient NOx levels and bus frequency are needed. In Scenario 1, there are many buses but still high pollution levels. This may be because of topographic conditions, or because the buses or factories are very polluting. In Scenario 2, air quality is good despite low bus frequency, possibly for the opposite reasons.
This suggests that, for any environmental issue, one should really look at multiple indicators for each issues, e.g. NOx emissions, and various responses to NOx emissions. However in practice this tends to be infeasible in terms of resources and funding.
A key role of SEA is to ensure that planners consider 1. the full range of desired outcomes, and 2. the full range of realistic inputs to achieve them. The topics listed at Unit 3 - air, water, soil etc. - suggest some of the outcomes that a strategic action may ultimately want to achieve.
The same outcome can often be achieved through different means/inputs, which in turn may have very different environmental impacts. For instance, people can be kept warm (social outcome) through more power stations or better insulation in people's houses, but power stations will have much greater impacts on air quality and the landscape than insulation. Planners often focus very quickly on inputs (Park and Ride sites, new road to bypass Town X, electric vehicles for all council employees) without checking whether other, less environmental damaging, inputs exist. SEA should test whether there are other means of achieving the same outcomes.
Planners also often make assumptions about the links between input and outcomes. But it may be worthwhile, through the SEA process, to check that these links really are there: Will new buses really attract people out of their cars? Will they really have cleaner emissions than the cars they replace?