Odzala National Park was created in 1935 (gazetted 1940), covering then 1,266 km². The Odzala complex also included the Lékoli–Pandaka Faunal Reserve (682 km²) and Mboko Hunting Reserve (900 km²), both to the south of the park. These and an enormous area of forest to the north, west and east of the original complex have been included in an enlarged National Park in June 2001. Odzala is on the southern fringes of the block of Guineo–Congolian forest extending from Gabon to DR Congo. The southern section of the site consists of a forest-savanna mosaic on a plateau at 500–600 m, while the north is continuous forest. Over 90% of the forest is semi-evergreen, with a fairly open canopy and a dense Marantaceae understorey; most of the rest is taken up by swamp-forest (with a closed canopy and more open understorey, Raphia is dominant very locally). Savannas occupy c.420 km² in the south, most of which is wooded grassland (with Hymenocardia acida, 2–4 m tall, as the main tree). There are also some thickets while many dambos (seasonally wet grassland) line the galleries of swamp-forest. Wetlands are small, but include rivers, small pools, Cyperaceae marsh and saltpans.
See Box and Table 2 for key species. Some 440 bird species have been recorded, of which c.330 are proven or thought to breed. Species of interest include Phoeniculus castaneiceps (previously unknown from the southern fringe of the Guineo–Congolian forest block), Smithornis sharpei, Lobotos oriolinus, Phylloscopus budongoensis and Apalis jacksoni (the latter two are mainly montane elsewhere), Cisticola eximius (previously unknown from south of the Guineo–Congolian forest block) and Ploceus dorsomaculatus. The yellow-bellied form of Stiphrornis erythrothorax (described as a new species S. sanghensis) is locally common (see site CG001). Falco naumanni and Glareola nordmanni are recorded as vagrants while Gallinago media is also known to occur and may prove to be regular on both passages. In addition, two species of the Zambezian biome (A10), Hirundo rufigula and Sylvietta ruficapilla, occur (the first as a seasonal migrant, the second is resident in wooded savanna).
Non-bird biodiversity: The park is an important refuge for large mammals, including Loxodonta africana (EN), Syncerus caffer nanus (LR/cd), Tragelaphus euryceros (LR/nt) (local), many primates, including Gorilla gorilla (EN) and Pan troglodytes (EN), and a small, isolated population of Panthera leo (VU). The forest vegetation is varied and has recently yielded a new species of Diospyros (D. whitei).
Pressure/threats to key biodiversity
Since 1992, the park has been administered by the European-funded Ecofac Project. This has brought about a significant decrease in the poaching of Loxodonta africana, but whether this improvement can be sustained beyond the life of the project is uncertain. The park has been considerably enlarged recently (2001); it used to fall within timber concessions, but no licences have ever been issued and all but one of the concessions have been withdrawn recently. The amount of big-game hunting that has taken place (in some years) in Mboko Hunting Reserve, and illegal hunting there and elsewhere, seem to have had no impact on bird populations. From June 1997, when the civil war spread from Brazzaville to the whole country, Ecofac had to reduce its activities to a minimum, mainly concerned with anti-poaching control, but by mid-1999 other activities were being resumed.