The habitat types found in the Peruvian Amazon resulted from large-scale geologic events during the tertiary and quaternary periods. The Samiria River basin sits in the Pevas lake bed, which formed during the uplifting of the Andes, and leaving a geological depression characterized by soft alluvial soils. This depression in western Amazonia allows the vegetated landscape to transform into the flooded forest that the region is known for. The Amazonian rainforest, including regions of Peru, is responsible for 20% of the oxygen on the entire planet.
Flora: Some of the native plant species present in the reserve are: Spondias mombin, Quararibea cordata, Mauritia flexuosa, Parinari excelsa, Cedrela odorata, Ocotea spp., Myrciaria dubia, Socratea exorrhiza, Calathea allouia, Solanum sessiliflorum, Hevea guianensis, Pouteria caimito, Clidemia hirta, Ficus maxima, Heliconia psittacorum, Inga spp., Psychotria poeppigiana, Alibertia edulis, Victoria amazonica, Ceiba pentandra, Phytelephas macrocarpa, Clusia spp., Swietenia macrophylla, Asclepias curassavica, Pachira aquatica.
Fauna: Mammal species found in the reserve include: the Amazonian manatee, the red-faced spider monkey, the South American tapir, the Bolivian squirrel, the Amazon river dolphin, the puma, the giant otter, the white-lipped peccary, the jaguar, the red brocket, the tucuxi, the South American coati, the capybara, etc.
Some species of fish found in the reserve are: Arapaima gigas, Pseudoplatystoma fasciatum, Phractocephalus hemiliopterus, Colossoma macropomum, Osteoglossum bicirrhosum, Potamotrygon motoro, Brycon melanopterus, Hyphessobrycon erythrostigma, Plagioscion squamosissimus, Prochilodus nigricans.
BIRDING: Special birds almost impossible to see elsewhere:
Wattled Curassow & Zimmer's Woodcreeper.
Restricted Range species: Black-tailed Antbird.
Good birds recorded at Yanayacu: Rufous-headed Woodpecker, Rufous-capped Nunlet, Scaled Spinetail, Orange-fronted Plushcrown, Dusky-chested Flycatcher.
Varzea/Igapo specialties: Plain-breasted Piculet, Rufous-capped Nunlet, Slender-billed Xenops, Amazonian Antshrike, Plumbeous Antbird, Yellow-crowned Elaenia, Royal Flycatcher, Dusky-tailed Flatbill, Varzea Mourner, Gray-chested Greenlet.
Terra Firme: Black-throated Trogon, Bluish-cheeked Jacamar, Rufous-necked Puffbird, Chestnut-capped Puffbird, Collared Puffbird, Bar-bellied Woodcreeper Spot-throated Woodcreeper, Saturnine Antshrike, Wire-tailed Manakin, Dot-backed Antbird.
Mauritia palm stands: Point-tailed Palmcreeper, Sulphury Flycatcher, Red-bellied Macaw.
Nightbirds: Zig-Zag Heron, Boat-billed Heron, Great Potoo, Long-tailed Potoo, Spectacled Owl.
On the water-conspicous birds: Horned Screamer, Black-collared Hawk, Green Ibis, Sungrebe, 5 species of Kingfishers, Slate-colored Hawk, White-eared Jacamar, Wattled Jacana, Hoatzin, Velvet-fronted Grackle, Red-and-white Spinetail, Plum-throated Cotinga, Band-tailed Oropendula.
Parrots: Blue-and-Yellow Macaw, Rose-fronted Parakeet, Festive Parrot and Short-tailed Parrot.