Satellites • Other remote sensing techniques • Saltmarsh morphology • Vegetation • Species specific studies

Species specific studies

Habitats and vegetation patterns are not the only features that require monitoring. Some species have special significance either because of their rarity, special habitat requirements or economic significance. Three elements (Keddy, 1991) can be discerned when monitoring individual species:

• A species is rare or of special interest and managed to protect the population. Monitoring is undertaken to determine if we being successful;
• The species is invasive (and undesirable) and we need to assess if our control measures are effective; and
• The species provides an indicator of change in the environment.

The expansion of Spartina anglica into many saltmarshes throughout the temperate regions of the world is a particularly important issue for saltmarsh and estuarine conservation. Studying this species should be relatively easy, as it occurs as an extensive monoculture in most of the areas where it has invaded. Airborne mapping would be particularly suitable for monitoring the spread of this species.

Establishing the location and population numbers of species, e.g. birds (especially breeding birds) or invertebrates, is also an essential prerequisite when seeking to establish the ecological value of a saltmarsh. It is important to know where the majority of a population of a species of conservation or commercial significance resides during critical periods of its life cycle. In saltmarshes, many species rely on a particular place in the marsh zonation (e.g. oystercatchers nest above the mean high water mark, where their nests are less likely to be flooded). Other species rely on the nature of the vegetation (e.g. a close-cropped sward is essential for grazing by the sometimes large and significant populations of winter ducks and geese).

Several shore bug species (e.g. Saldidae, ground dwelling predators) live in different parts of the marsh. Saldula pilosella lives at the margins of sheltered pools on the upper shore, Saldula littoralis in dense vegetation and Saldula palustris occurs on more open sandy/muddy areas, extending further down the marsh than the other species (Kirby, 1992). Other invertebrates may rely on a single plant species for their survival and in some cases different parts of a single plant. Monitoring these species requires specialists in the monitoring techniques for each species or group of species (such as insects or birds).