Although the data collected for project EIA can be very comprehensive and detailed, it is simply not efficient, necessary, or physically possible to do this for SEA. Choices must be made about what is necessary and feasible.
The is a difference between data and the information they provide for decision-makers. Some data may be beautifully, intricately monitored over a long time period, and look wonderful in the SEA baseline, but may provide no useful information for SEA or decision-making. Examples are:
- car ownership: is increased car ownership good because it is a sign of economic prosperity or bad because it indicates unsustainable lifestyles?
- land area taken up by nature conservation designations: given that there are no standards for what area should be taken up by designations, what does this say?
- GDP: traditionally this has been used to describe people's quality of life, but it has been increasingly discredited in that sense. Useful for economic purposes, but probably not for SEA.
- trends: ("in 1990 it was 13 hectares" is very different from "in 1990 it was 130 hectares");
- comparison against targets or standards ("50 hectares would be needed to allow the big-eared dickybird to be re-introduced");
- comparison against other areas: "the residents of authority X have less than half the area of woodland per person than adjacent authorities Y and Z".
For example, here is basic data about air pollution levels at four locations...
|Location||acid dep. keq/ha/yr||ammonia ug/m3||N deposit. kg N/ha/yr||NOx ? NO2/m3||Ozone ppb hours||SO2 ug/m3|
... and here is the same data, but interpreted in relation to the air pollution levels that the habitats at those locations can withstand. Which is more useful for decision-making?
|Location||acid dep.||ammonia||N deposit.||NOx||Ozone||SO2|