Forest (2000)

To advance our understanding of forest cover changes, given the discrepancies, this work provides an original analysis by assessing five available remote sensing datasets (ALOS PALSAR forest and non- forest data, ESA CCI Land Cover, MODIS IGBP, Hansen/GFW on global tree cover loss, and Terra-I) to estimate the likely extent of current forests (circa 2018) and forest cover loss from 2001-2018, for which data was available. This assumes that no single approach or data source can capture major trends everywhere; therefore, an all-available data approach is needed to overcome shortcomings of individual datasets. The main shortcomings of this approach, however, are that it does not account for forest gains, tends to underestimate the conversion in dry forests ecosystems and lacks explicit assessment of uncertainties across the different datasets. “Forest cover loss” in the all-available data analysis consists of observations (pixels) changing from forest to non-forest at any time during 2000 to 2018. The spatial resolution chosen was 250m given the original resolutions of the datasets incorporated and on the understanding that forest areas should be a minimum of 250 x250m (6.25 ha) to contain the functional attributes of a forest (e.g. species distribution, ecology, ecosystem services), rather than depicting individual trees or groups of trees. According to our analysis, about 20% of total forest cover loss takes place in core forest, which we label “primary forest loss”, while the remaining 80% results from the conversion of edge and patched forests, which is labelled as “secondary forest loss”. Two thirds of total forest cover loss in the period from 2000-2018 occurred in the tropics and subtropics, followed by boreal and temperate forests. A portion of the loss in temperate and boreal forests will not be permanent and might refer to other types of natural forest disturbances produced by insects, fire, and severe weather, as well as by felling of plantations or semi-natural forests as part of forest management. Much tropical forest cover loss is in South America and Asia, while subtropical forest cover loss is mainly in South America and Africa. When looking at countries by income levels, as defined by the World Bank, much of deforestation takes place in upper middle and lower middle-income countries. To the risk of simplifying, this suggests an increasing pressure on forests in the transition that occurs when countries increase economic development. In the tropics, upper-middle income countries dominate forest cover loss in South America, due to the influence of Brazil, and lower middle- income countries in Asia, due to the influence of Indonesia. Forest cover loss in the subtropics occurs mainly in Brazil and Argentina in South America, many lower-middle income countries in South America, and lower-income countries in sub-Saharan Africa. Most temperate and boreal forest cover loss, likely not all permanent, occurs in high-income countries (Russia), and North America (United States and Canada) Unfortunately, this data does not identify changes over time or land use interactions among countries. Reduced forest cover loss in some mainly high-income countries, except North America, is associated with forest cover loss, particularly in lower- and upper-middle countries in the tropics. Interactions are informed by the “forest transition” effect. Forest transition dynamics occur when net forest restoration replaces net forest cover loss in some specific place. The countries that underwent a forest transition that reduced forest loss and encouraged regrowth may have placed additional pressure on forests outside their borders, thus displacing deforestation. The debate on forest transitions and leakage is quite controversial given its policy implications. Recent analysis, based on a land-balance model that quantifies deforestation due to global trade at country level in the tropics and sub-tropics, linked to a country-to-country trade model, found that from 2005-2013, 62% of forest loss was caused by commercial agriculture, pasture and plantations. About 26% of total deforestation was attributed to international demand, 87% of which was exported to countries with decreasing deforestation or increasing forest cover in Europe and Asia (i.e. China, India). Some of this displacement pressure may be reduced by land intensification. Global patterns of forest fragmentation In this analysis we consider forest degradation alongside forest cover loss. Degradation is a multi- factorial phenomenon that includes amongst others loss of native species, appearance of invasive species, pollution damage, structural changes, selective timber removal and many more. Here we use fragmentation as a proxy that can be detected through remote sensing; this is a critical aspect of forest degradation but does not capture all aspects. The change in spatial pattern and structure by fragmentation of forest into smaller patches or “islands” damages forest ecosystem services such as carbon storage and climate mitigation, regulation, water provision, and habitat for biodiversity. These impacts are created by changes at forest edges, which include increased exposure to different climate, fire, wind, mortality, and human access. The increasing isolation of forest patches contributes to long-term changes in biodiversity, including species richness and productivity, creating fundamental changes in forest ecosystems. We evaluated the fragmentation of forests using morphological spatial pattern analysis (MSPA) assessed on the two all-available data global forest cover maps corresponding to 2000 and 2018, to determine forest cover transitions between different type of fragmentation classes (i.e. stable core, inner edges, outer edges, and patches). Changes between fragmentation classes over time are defined as primary and secondary degradation based on their initial state, in contrast to forests which remain in the same fragmentation class as stable core, inner edge, outer edge, and patch. In this definition, primary degradation is a result of the fragmentation of core forests into forest with more edges, reducing the area of continuous forest extent, and resulting in greater losses of carbon and associated ecosystem services such as biodiversity present in intact forests. Secondary degradation is the conversion of edge forests into more fragmented classes, occurring in secondary forests which may already be degraded and are more accessible and easier to deforest