Timor-Leste includes the mountainous eastern half of Timor, the Ocussi-Ambeno region on the northwest portion of the island of Timor, and the islands of Atauro and Jaco. The country is located northwest of Australia in the Lesser Sunda Islands at the eastern end of the Indonesian Archipelago. 'Timor' is a Portuguese derivation of 'Timor', the Malay word for "Orient"; the island of Timor is part of the Malay Archipelago and is the largest and easternmost of the Lesser Sunda Islands. Timor-Leste is the only Asian nation to lie entirely within the Southern Hemisphere. The Loes River is the longest with a length of . This river system covers an area of . It is a small country with a land size of . The exclusive economic zone is .
Timor-Leste's fauna is diverse and contains a number of endemic and threatened species. The Timor and Wetar deciduous forests region, which covers the entire island, has 38 mammal species. Timor-Leste's two endemic mammal species are the Timor shrew and the Timorese horseshoe bat. The country's and region's largest mammal, the Javan rusa, and its only native marsupial, the Northern common cuscus, are both believed to have been introduced to the island in prehistoric times by settlers from the Lesser Sunda Islands and New Guinea, respectively. Other mammals found in Timor-Leste include the Crab-eating macaque, a large number of species of bats, and the aquatic mammal, the Dugong. Timor-Leste also has its own native horse breed, the Timor pony.
Timor-Leste's terrestrial biodiversity is most visible in its native bird species. As of 2022, a total of 289 bird species are found in Timor-Leste. Significantly threatened bird species include the endangered Timor green pigeon and Wetar ground dove and the critically endangered Yellow-crested cockatoo. Timor-Leste has an endemic subspecies of the Iris lorikeet, S. i. rubripileum.
Along with the Solomon Islands, Papua New Guinea, the Philippines, Indonesia, Malaysia and Australia, Timor-Leste is one of the countries located in the Coral Triangle, the site of the most biodiverse coral reefs in the world. In particular, Atauro Island's coral reefs have been recognised as having the highest average fish biodiversity of any site surveyed, with reef sites off Atauro carrying an average of 253 different species. The highest number of species recorded from a single site in Timor-Leste was 642 different fish species, ranking second out of surveyed sites after Indonesia's Raja Ampat Islands.
Additionally, the reefs appeared to have suffered limited damage from coral bleaching and rising ocean temperatures compared to other sites in the Coral Triangle. However, despite being in relatively pristine condition, the reefs remain threatened by climate change and habitat destruction, especially blast fishing. It is believed that this has most affected large marine species such as sharks; despite the diversity of the reefs, there were a significant lack of sharks recorded in the surveys of 2016.
Timor-Leste's isolation and lack of tourism are believed to have helped preserve the reefs, as opposed to tourist-heavy locales such as Bali, where the abundance of tourism has negatively affected the health of the reefs. The Timorese government and local residents of Atauro have made attempts to preserve the reefs through education of local citizens, rejecting harmful development projects, and placing emphasis on traditional laws of preserving nature, called Tara Bandu.
Global Forest Watch publishes annual estimates of tree cover loss and 2000 tree cover extent derived from time-series analysis of Landsat satellite imagery in the Global Forest Change dataset. In this framework, tree cover refers to vegetation taller than 5 m (including natural forests and tree plantations), and tree cover loss is defined as the complete removal of tree cover canopy for a given year, regardless of cause.
For Timor-Leste, country statistics report cumulative tree cover loss of from 2001 to 2024 (about 4.6% of its 2000 tree cover area). For tree cover density greater than 30%, country statistics report a 2000 tree cover extent of . The charts and table below display this data. In simple terms, the annual loss number is the area where tree cover disappeared in that year, and the extent number shows what remains of the 2000 tree cover baseline after subtracting cumulative loss. Forest regrowth is not included in the dataset.
Under the UNFCCC REDD+ framework, Timor-Leste has submitted a national forest reference level (FRL). On the UNFCCC REDD+ Web Platform, the country's 2023 submission is listed as having an assessed reference level, while a national strategy, safeguards information and a national forest monitoring system are all listed as "not reported".
The first assessed FRL, submitted in 2023, covered the REDD+ activities "reducing emissions from deforestation" and "enhancement of forest carbon stocks" at national scale. Using a 2017-2021 reference period, the original submission proposed -215,868 t CO2 eq per year, revised during the technical assessment to an assessed FRL of -196,723 t CO2 eq per year. The technical assessment states that it included above-ground biomass and below-ground biomass, reported CO2 only, and used a forest definition of at least 0.5 hectares, 15 percent canopy cover, and trees of actual or potential height greater than 5 metres.