Peat formation is primarily a function of climate. Peatland distribution is therefore concentrated in specific climatic regions.
Climate determines the amount of water available in the landscape via the amount of net precipitation, while temperature affects both the production and decay of organic material. Accumulation and maintenance of peat is only possible when the balance between production and decay is positive. Peatlands are therefore especially abundant in cold (i.e. boreal and sub-arctic) and wet (i.e. oceanic and humid tropical) regions. In areas where the precipitation/evaporation balance is less favourable for accumulation, peatlands are only found where landscape features enable water to collect. The scarcity of peatlands in the southern hemisphere is due to the absence of land in the relevant climatic zones. In mountains, zonation in altitude reflects the zonation in latitude.

Peatlands prevail on flat surfaces.
As water-logging requires a flat surface, large peatlands prevail on extensive flat land areas, such as western Siberia, the Hudson Bay Lowlands (Canada), the Southeast Asian coastal plains, and the Amazon Basin. In areas with abundant water supplies and limited water loss, peatlands may also occur on slopes. It is these conditions that can produce blanket bogs and hill slope peatlands.

Approximately 4 million km2 of the Earth (some 3% of the land area) is covered with peatland (with >30 cm of peat). Peatlands are found in almost every country of the world.
Peatlands (with >30 cm of peat) cover approximately 4 million km2 (Joosten and Clarke 2002, Lappalainen 1996, cf. Rubec 1996, Zoltai and Martikainen 1996). Peatlands with less than 30 cm of peat may cover an additional 5 - 10 million km² (Tjuremnov 1949, Vompersky et al. 1996) and are largely situated in the permafrost regions (Vompersky et al. 1996). Countries with the most extensive peatland area include Russia, Canada, the USA and Indonesia. Together, these countries hold over 60 % of the global peatland area (Joosten and Clarke 2002). No peatlands are as yet known in Libya, Somalia, Saudi-Arabia, Yemen, Oman, Jordan, and Turkmenistan (IMCG Global Peatland Database).

The general inventory status of peatlands is (largely) inadequate.
For some regions almost nothing is known about peatlands. This is the case, for example, for large parts of Africa and South America and for the mountain areas of central Asia. Major problems preventing a consistent global overview include a lack of awareness and capacity, typological differences between countries and disciplines, different inventory scales and the use of outdated data.