Indicator 15.4.2 Mountain Green Cover Index

Indicator 15.4.2: (a) Mountain Green Cover Index and (b) proportion of degraded mountain land

Target 15.4: By 2030, ensure the conservation of mountain ecosystems, including their biodiversity, in order to enhance their capacity to provide benefits that are essential for sustainable development

Food and Agriculture Organization of the United Nations (FAO)

Definitions:

The indicator is composed of two sub-indicators to monitor progress towards the conservation of mountain ecosystems:

Sub-indicator 15.4.2a, Mountain Green Cover Index (MGCI), is designed to measure the extent and changes of green cover - i.e. forest, shrubs, trees, pasture land, cropland, etc. – in mountain areas. MGCI is defined as the percentage of green cover over the total surface of the mountain area of a given country and for given reporting year. The aim of the index is to monitor the evolution of green cover and thus assess the status of conservation of mountain ecosystems.

Sub-indicator 15.4.2b, Proportion of degraded mountain land, is designed to monitor the extent of degraded mountain land as a result of land cover change in a given country and for given reporting year. Similarly to sub-indicator ‘’trends in land cover” under SDG Indicator 15.3.1 (Sims et al. 2021), mountain ecosystem degradation and recovery is assessed based on the definition of land cover type transitions that indicate improving, stable or degrading conservation status. The definition of degradation adopted for the computation of this indicator is the one established Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES)^[1].

Concepts:

Mountain area is defined according to the UNEP-WCMC (2002) method. It defines total global mountain area as the sum of seven classes (commonly known as ‘Kapos mountain classes’), based on elevation, slope and local elevation ranges (Table 1).

Table 1. Global mountain classes as defined by UNEP-WCMC (2002)

Prior to the methodological refinement of this indicator approved by the Inter-agency and Expert Group on SDG Indicators (IAEG-SDG) in June 2022, the UNEP-WCMC classification was used to disaggregate the indicator by Kapos mountain classes. This is no longer the case, with Kapos mountain classes having been replaced by a bioclimatic belts (see section 2.c below).

Land cover refers to the observed physical cover of the Earth’s surface. It includes vegetation and man-made features as well as bare rock, bare soil and inland water surfaces (FAO-GTOS, 2009). The primary units for characterizing land cover are categories (e.g. Forest or Open Water). These categories must be defined following a standardized land cover classification in order to identify land cover changes consistently over time. Several global standards of land cover classifications have been developed by international initiatives for this purpose.

For the purposes of standardization and harmonization when reporting on SDG Indicator 15.4.2, this indicator has adapted the land cover classification established by the United Nations Statistical Commission’s System of Environmental and Economic Accounting (UN-SEEA) (UN Statistical Division, 2014) by selecting the most relevant SEEA classes for mountain ecosystems and aggregating all croplands classes (Table 2).

Table 2. Left: Land cover classification established by the UN-SEEA (Source: UN Statistical Division, 2014). Right: Adapted land cover classification for the computation and aggregate reporting on SDG Indicator 15.4.2.

Land cover serves different functions for SDG Indicator 15.4.2:

In sub-indicator 15.4.2a, land cover is used to categorize land into green and non-green cover areas. As showed in Table 3, green cover includes areas covered by both natural vegetation and vegetation resulting from anthropic activity. Non-green areas include non-vegetated areas such as bare land, water, permanent ice/snow, urban areas and sparsely vegetated areas. In addition, land cover is used to disaggregate the indicator into the 10 land cover classes included in Table 2, thus increasing the indicator’s policy relevance.

Table 3. Classification of SEEA land cover classes into green and non-green cover.

In sub-indicator 15.4.2b, land cover is used to identify areas where changes in the type of land cover (land cover transitions) may indicate a decline or loss of biodiversity, mountain ecosystem functions or services that are considered desirable in a local or national context. A transition that indicates a decline or loss of biodiversity and mountain ecosystem services of the land is considered degradation. The definition of land cover transitions is documented in a transition matrix that specifies the land cover changes occurring in a given land unit (pixel) as being either degradation, improvement or neutral transitions.

Both sub-indicators will be expressed as proportions (percent) and area (KM2).

Land cover maps developed by appropriate national authorities will generally provide the most relevant data source to compute this indicator. However, in certain cases, such data may not be available. In those cases, various regional or global products provide a viable alternative.

The global default source of land cover data for this indicator is the European Space Agency Climate Change Initiative (ESA-CCI) Land Cover product (ESA, 2017). The ESA-CCI product consists of a series of annual Land Cover maps at 300 m resolution, providing 22 land cover classes based on 300m MERIS, 1km SPOT –VEGETATION, 1km PROBA –V and 1km AVHRR. The ESA CCI adheres to the FAO Land Cover Classification System (Santoro et al. 2015). Annual updates are currently available from 1992 to 2020. Additional years will be made available by the European Space Agency.

A global mountain area map sub-divided by bioclimatic belts has been developed by FAO and made available to national authorities to facilitate the compute this indicator. This map is the result of combining a global mountain area map developed from the Global Multi-Resolution Terrain Elevation Data (GMTED2010), following the UNEP-WCMC methodology (Ravilious et al. 2021) and a mountain bioclimatic belt map created by the Global Mountain Biodiversity Assessment^[2].

NSO SDG focal points will provide reports that include values for both sub-indicators, including the original data and reference sources, and descriptions of how these have been used to derive sub-indicators values. FAO will provide country-specific values for both sub-indicators when national official data do not exist or are incomplete, in consultation with concerned countries

The indicator can be calculated using freely available Earth Observation data and simple Geographic Information Science (GIS) operations that can be processed in free and open source software (FOSS) GIS. Regional and global land cover data derived from Earth observation can play an important role in the absence of, to complement, or to enhance national official data sources. These datasets can help validate and improve national statistics for greater accuracy by ensuring that the data

Recognizing that this indicator cannot fully capture the complexity of mountain ecosystems across the world, countries are strongly encouraged to use other relevant national or sub-national indicators, data and information to strengthen their interpretation, as well as taking into account the following limitations:

• Sub-indicator ‘’a’’ should be interpreted with care given that: 1) lack of green cover does not necessarily mean that a particular mountain area is degraded (i.e. areas of permanent snow and ice, scree slopes and natural sparsely vegetated areas above the tree line, 2) it does not capture significant drivers of change such as conversion of natural areas to cropland or pastureland, and 3) increase in green cover may due to impacts of climate change in mountain areas (i.e. increase in green cover due to snow and glacier retreat due to global warming).
• Because land cover refers to the naturally stable aspects of land and the structure of its key elements, transient aspects such as vegetation phenology, snow or flooding cannot be captured by land cover transitions as measured in sub-indicator 15.4.2b. In the context of SDG Target 15.4, this is particularly relevant for snow cover dynamics (snow cover duration within a year), which has been highlighted as a key impact of global warming in mountain ecosystems with direct impacts to water provision (Notarnicola, 2020).
• Decisions about which land cover transitions are linked to degradation processes would sometimes require information on the use of land, not only land cover. For example, the conversion of tree-covered areas to grassland may be a result of deforestation (change in land cover and land use) or just the result of certain management practices and natural disturbance (change in land cover only). The former could be identified as a negative transition, while the latter could be considered as stable or unchanging. The use of land use information would help to better characterize those changes in the context of sub-indicator “b’’.
• Both sub-indicators are not able to capture ecosystem degradation drivers that do not necessarily result in changes in land cover. Some examples of this include conversions of natural forests to intensively managed production systems such as plantation forests, orchards and oil palm plantations; conversion of natural and semi-natural grasslands to intensively used pastures, forest and grassland degradation or invasive species invasion, among others. However, the use of more detailed national land use maps may be able to overcome some of these gaps for sub-indicator 15.4.2b.
• While access to remote sensing imagery has improved dramatically in recent years, there is still a need for essential historical time series that is currently only available at coarse to medium resolution. Therefore, if countries have national land cover maps of higher spatial resolution and comparable or better quality, FAO advises using them, following the same methodology presented here, for the generation of the indicator’s values.
• Area estimations based on remote-sensing-derived land cover maps such as the ESA-CCI product via pixel counting may lead to biased area estimates due to map errors (Olofsson et al. 2014). Countries are encouraged to further refine those estimates by comparing them against reference datasets and applying bias corrections.

Sub-indicator 15.4.2a, Mountain Green Cover Index, is defined as:

$MGCI=\mathrm{\ }\frac{{Mountain\mathrm{\ }Green\mathrm{\ }Cover\mathrm{\ }Area}_n\mathrm{\ }}{Total\mathrm{\ }Mountain\mathrm{\ }Area}\times 100$

Where:

• Mountain Green Cover Area_n =Sum of areas (in km²) covered by (1) tree-covered areas, (2) croplands, (3) grasslands, (4) shrub-covered areas and (5) shrubs and/or herbaceous vegetation, aquatic or regularly flooded classes in the reporting period n.
• Total mountain area = Total area of mountains (in km²). In both the numerator and denominator, mountain area is defined according to UNEP-WCMC (2002).

Sub-indicator 15.4.2b, Proportion of degraded mountain area, is reported as a binary quantification (degraded/non-degraded) of the extent of degraded land over total mountain area, given by:

$Proportion\mathrm{\ }of\mathrm{\ }degraded\mathrm{\ }mountain\mathrm{\ }area=\frac{Degraded\mathrm{\ }mountain\mathrm{\ }area\mathrm{\ }n}{Total\mathrm{\ }mountain\mathrm{\ }area}\mathrm{\ }\times 100$

Where:

• Degraded mountain area_n = Total degraded mountain area (in km²) in the reporting period n. This is, the sum of the areas where land cover change is considered to constitute degradation from the baseline period. Degraded mountain land will be assessed based on the land cover transition matrix in Annex 1.
• Total mountain area = Total area of mountains (in km²). In both the numerator and denominator, mountain area is defined according to UNEP-WCMC (2002).

If the country/region has no mountain area, it will be assigned value NA.

2024-07-29

Food and Agriculture Organization of the United Nations (FAO)

6.6.1, 15.1.1, 15.2.1, 15.3.1, 15.4.1

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