Two major climatic regions meet within the transfrontier park, namely the warm temperate winter rainfall area, characteristic of the Succulent Karoo biome, and a non-seasonal rainfall region to the east, akin to the Nama-Karoo biome. The rainfall in the winter rainfall area (May - September) varies from 15 mm per annum in the valleys to 300 mm on the mountain tops. Chilly misty conditions are often caused by the Benguela anti-cyclone. In winter the temperature can drop to below 0°C, while in summer it can soar to 52°C, hence the appropriate name of the area: |Ai-|Ais, meaning “hot, very hot”.
The |Ai-|Ais/Richtersveld Transfrontier Park is a renowned geological classroom, featuring many distinct periods of geological history that span some 2 000 million years. Complex, intensely folded, fractured and actively uplifted landmasses are now heavily eroded. The Orange River mouth is a Ramsar site, and the 350-million-year-old erosion-rich lower Orange River gorge abounds with history, folklore and grandeur.
The area is renowned for housing most of the richest succulent flora of the world. The Orange River is characterised by striking endangered riparian bush. At the Gariep Centre of Plant Endemism, with the transfrontier park at its core, at least 2 700 species of plants, 560 of which are endemic or near-endemic, can be found. A soft but regular and therefore effective rainfall is mainly responsible for this abundance of plant life. Many of the endemic plants are limited to small areas, mostly on mountains where the rainfall is higher and habitat diversity is greatest. The best-known endemic plants are the stem succulents known as the “halfmens”, Pachypodium namaquanum, and the giant tree aloe, Aloe pillansii.
The animal species found in the area are adapted to withstand the harsh, arid climate. Other species are concentrated in the denser vegetation bordering the Orange River, including 56 species of mammals and 194 bird species. Furthermore, a large variety of lizards (35 species) and snakes (16 species) are found in various microhabitats.