National Land Cover Account methodology

Areas that have an artificial cover as a result of human activities such as construction (cities, towns, transportation), extraction (open mines and quarries) or waste disposal.

Areas where the natural vegetation has been removed or modified and replaced by other types of vegetative cover of anthropogenic origin. This vegetation is artificial and requires human activities to maintain it. In between the human activities, or before starting crop cultivation, the surface can be temporarily without vegetative cover. Its seasonal phenological appearance can be regularly modified by humans (e.g., tillage, harvest, and irrigation). All vegetation that is planted or cultivated with an intent to harvest is included in this class (e.g., wheat fields, orchards).

Areas where the dominant vegetative cover is below two metres in height and woody canopy cover is less than 20%. These areas would be dominated by crops or grasslands and shrubs.

The exposed intertidal zone consists of coastal regions periodically inundated by tidal flows, not including areas obscured by vegetation cover such as mangroves.

Areas which are transitional between pure terrestrial and aquatic systems and where the water table is usually at or near the surface, or the land is covered by shallow water. The predominant vegetation, at least periodically, comprises hydrophytes. Marshes, swamps, bogs or flats where drastic fluctuations in water level or high concentration of salts may prevent the growth of hydrophytes are all part of this class. The vegetative cover is significantly influenced by water and dependent on flooding (e.g., mangroves, marshes, swamps and aquatic beds). Occasionally-flooded vegetation within a terrestrial environment is not included in this class. Natural aquatic vegetation habitats are defined as biotopes where the vegetative cover is in balance with the influence of biotic and abiotic forces. Semi-natural aquatic vegetation is included in this class, defined as vegetation that is not planted by humans but which is influenced directly by human activities that are undertaken for other, unrelated purposes. Human activities (e.g., urbanization, mining and agriculture) may influence abiotic factors (e.g., water quality), affecting species composition. Furthermore, this class includes vegetation that developed due to human activities but which has recovered to such an extent that it is indistinguishable from its former state, or which has built up a new biotope which is in balance with the present environmental conditions. A distinction between natural and semi-natural aquatic vegetation is not always possible because human activities that are away from the habitat may nonetheless create chain reactions which ultimately disturb the aquatic vegetative cover. Human activities may also take place deliberately to compensate for effects as noted above with the aim of keeping a "natural" state. Only mangroves are included in the current release.

Areas that do not have an artificial cover as a result of human activities. These areas include areas with less than 4% vegetative cover. Included are bare rock areas, sands and deserts.

Areas where the vegetative cover is in balance with the abiotic and biotic forces of its biotope and includes semi-natural vegetation. Semi-natural vegetation is defined as vegetation not planted by humans but influenced by human actions. These may result from grazing, possibly overgrazing, or else from practices such as selective logging in a natural forest whereby the floristic composition has been changed. Previously cultivated areas which have been abandoned and where vegetation is regenerating are also included. The secondary vegetation developing during the fallow period of shifting cultivation is a further example. The human disturbance may be deliberate or inadvertent. Hence semi-natural vegetation includes vegetation due to human influences but which has recovered to such an extent that species composition and environmental and ecological processes are indistinguishable from, or in a process of achieving, its undisturbed state. The vegetative cover is not artificial, and it does not require human activities to be maintained in the long term.

Areas that are naturally covered by water, either naturally (such as lakes, rivers, snow or ice) or artificially (due to the construction of artefacts such as reservoirs, canals, artificial lakes, etc). In the case of rivers, the lack of vegetation cover is often due to high flow rates and/or steep banks. In the case of lakes, their geological origin affects the life conditions for aquatic vegetation. The following circumstances might cause water surfaces to be without vegetation cover: depth, rocky basins, rocky and/or steep shorelines, infertile washed-in material, hard and coarse substrates. Areas covered by water for less than nine months of the year are classed as Non-perennial.

Areas where the vegetative cover is at least two metres in height and has at least 20% canopy cover. These areas would be dominated by shrubs and trees.

Managed expansion represents an increase in the area of a land cover type due to human activity. For example, crop areas may be converted to tree-covered areas due to silvicultural measures such as planting and seeding, or tree-covered areas may be converted to crop or grassland following tree clearing. Generally, the managed expansion of one land cover type will also lead to the recording of a matching entry for managed regression of the reducing land cover types.

Managed regression represents a decrease in the area of a land cover type due to human activity.

Other expansions and regressions represent change in land cover type that cannot be attributed to human activity. That is, they are either natural changes or there is insufficient data to determine the reason for change.

Managed expansions and regressions and Other expansions and regressions were estimated using data in the Artificial surfaces and Cultivated terrestrial vegetated: Herbaceous classes. The assumption was made that changes to or from these classifications were managed changes, with all other changes categorised as other changes.

An increase in the area or value of the stock of land. The change could be due to purchases of land for other uses, reassessment of land type or natural encroachment of other land covers.

Physical or monetary stock at the end of the reference period.

A unit of area equal to 10,000 square metres.

The observed physical and biological cover of the land surface and includes natural vegetation, inland waters and abiotic (non-living) surfaces. Coastal waters are excluded. The land cover is a function of natural changes in the environment and of previous and current land use, particularly in agricultural and forestry areas. The land cover classes included in this release are:

• Artificial surfaces
• Cultivated terrestrial vegetated: Herbaceous
• Cultivated terrestrial vegetated: Woody
• Natural terrestrial vegetated: Herbaceous
• Natural terrestrial vegetated: Woody
• Natural surfaces
• Natural aquatic vegetated: Herbaceous
• Natural aquatic vegetated: Woody
• Water: Perennial
• Water: Non-perennial
• Tidal area

Descriptions of these classes can be found in the Classifications section.

An increase in the area of a land cover type due to human activity.

A decrease in the area of a land cover type due to human activity

The change between the reference periods in physical or monetary units. The change can be positive or negative.

Physical or monetary stock at the beginning of an accounting period.

An increase in land cover type that cannot be attributed to human activity. That is, they are either natural changes or there is insufficient data to determine the reason for change.

A decrease in land cover type that cannot be attributed to human activity. That is, they are either natural changes or there is insufficient data to determine the reason for change.

Represents a decrease in the area for the stock of land. These changes could be due to sales of land for other uses, reassessment of land type or natural encroachment of other land covers.