We seek information and manage natural systems at a wide range of scales in time and space and must take this into account when selecting indicators. For example, minesite rehabilitation occurs over fairly small areas, while ozone depletion has a global scale. Minesite rehabilitation may respond to management intervention within 5 to 10 years; but ozone depletion may take decades to respond to reduced use of depleting substances.

Minesite rehabilitation can be based on sensitive analysis of the landscape desired. Indicators can confirm progress towards the goals. These photographs are 2 and 4 years after establishment of native tree species.

Some natural processes are extremely brief, but many operate on time scales from decades to centuries (for example, some trees live for 500 years). In contrast, environment management programs often operate on time-frames of a few years, making it difficult to select indicators to assess their success.

Often we will have to select indicators with an assumed link to environmental outcomes (for example, the success in establishing perennial deep-rooted plants to address rising water tables). For long-term purposes, the actual environmental outcomes should also be monitored (in this example, what actually happens to the water table).

Management decisions are often made on different space scales to the systems being managed. For example, local government boundaries may be the main basis of management of something that involves an ecological scale - such as a river catchment covering several local government areas or even crossing State boundaries. So, the indicator selected must be relevant at the catchment scale, but also meaningful at local and other government scales.

Some environmental issues must be assessed at each of local, state and national levels, but managers at these scales may need different information. For example, a farmer needs to know how much soil is being lost to erosion in a particular field, while a national agency needs to know the extent of erosion country-wide.

Different indicators may therefore be needed for managers operating at different scales. They may often be based on the same data, and finding reliable ways to aggregate, or disaggregate, data across space scales is a continuing and difficult challenge. The challenge is even greater when linking both space and time considerations. Expert assistance may be needed to underpin indicator-related action at local to global levels.