In the north it is bounded to the west by a stretch of South American Pacific mangroves and to the east by Northwestern Andean montane forests.

Further south the ecoregion reaches the Pacific Ocean to the west, and adjoins Eastern Cordillera Real montane forests to the east.

Further south again it is bordered by Sechura Desert to the west and to the east by patches of Marañón dry forests, Peruvian Yungas and Cordillera Central páramo.

Higher up the soils are made of Precambrian amphibolites, Paleozoic granites, Devonian quartzites and black slate, and Carboniferous dark limestone, sandstone and lutites.

Common species in the dry forests include Loxopterygium huasango, Handroanthus billbergii and holy wood (Bursera graveolens), all threatened by human exploitation.

Other common species are Ziziphus thyrsiflora, Caesalpinea corymbosa, Capparis angulata, Bombax discolor, Pitthecellobium multiflorum and Geoffroya striata.

The area is rich in mesquite (Prosopis genus), which capture and fix nitrogen in their roots, enriching the soil and assisting other species.

[1] Endangered birds include grey-cheeked parakeet (Brotogeris pyrrhoptera), grey-backed hawk (Pseudastur occidentalis), rufous flycatcher (Myiarchus semirufus), slaty becard (Pachyramphus spodiurus), white-winged guan (Penelope albipennis), Peruvian plantcutter (Phytotoma raimondii), El Oro parakeet (Pyrrhura orcesi), yellow-bellied seedeater (Sporophila nigricollis), Peruvian tern (Sternula lorata) and blackish-headed spinetail (Synallaxis tithys).

Birds with limited distribution include white-tailed jay (Cyanocorax mystacalis) and red-masked parakeet (Psittacara erythrogenys).

This included capture of parrots and parakeets for sale as pets, hunting some mammals and reptiles for food, and extraction of wood for firewood, charcoal and timber.