The Lacandon Jungle (Spanish: Selva Lacandona) is an area of rainforest which stretches from Chiapas, Mexico, into Guatemala. The heart of this rainforest is located in the Montes Azules Biosphere Reserve in Chiapas near the border with Guatemala in the Montañas del Oriente region of the state. Although much of the jungle outside the reserve has been cleared, the Lacandon is still one of the largest montane rainforests in Mexico. It contains 1,500 tree species, 33% of all Mexican bird species, 25% of all Mexican animal species, 56% of all Mexican diurnal butterflies and 16% of all Mexico's fish species. The Lacandon in Chiapas is also home to a number of important Mayan archaeological sites including Palenque, Yaxchilan and Bonampak, with numerous smaller sites which remain partially or fully unexcavated. This rainforest, especially the area inside the Biosphere Reserve, is a source of political tension, pitting the EZLN or Zapatistas and their indigenous allies who want to farm the land against international environmental groups and the Lacandon Maya, the original indigenous group of the area and the one that holds the title to most of the lands in Montes Azures. The jungle has approximately 1.9 million hectares stretching from southeast Chiapas into northern Guatemala and into the southern Yucatán Peninsula. The Chiapas portion is located on the Montañas del Oriente (Eastern Mountains) centered on a series of canyonlike valleys called the Cañadas, between smaller mountain ridges oriented from northwest to southeast. It is bordered by the Guatemalan border on two sides with Comitán de Domínguez to the southwest and the city of Palenque to north. Dividing the Chiapas part of the forest from the Guatemalan side is the Usumacinta River, which is the largest river in Mexico and the seventh largest in the world based on volume of water. The core of the Chiapas forest is the Montes Azules Biosphere Reserve, but it also includes some other protected areas such as Nahá–Metzabok, Bonampak, Yaxchilan, Chan-Kin, Lacan-Tun, and the communal reserve of La Cojolita.