The Lombok Strait lies to the immediate west of the island, marking the passage of the biogeographical division between the prolific fauna of the Indomalayan ecozone and the distinctly different, but similarly prolific, fauna of Australasia�this distinction is known as the "Wallace Line" (or "Wallace's Line") and is named after Alfred Russel Wallace. Wallace was the first person to comment on the division between the two regions, as well as the abrupt boundary between the two biomes.
To the east of Lombok lies the Alas Strait, a narrow body of water separating the island of Lombok from the nearby island of Sumbawa to the east.
The island's topography is dominated by the centrally-located stratovolcano Mount Rinjani, which rises to 3,726 m (12,224 ft), making the second highest volcano in Indonesia and the nation's third-highest mountain. The most recent eruption of Rinjani was in May, 2010 at Gunung Barujari. Ash was reported as rising up to two km into the atmosphere from the Barujari cone in Rinjani's caldera lake of Segara Anak. Lava flowed into the caldera lake, pushing its temperature up and crops on the slopes of Rinjani were damaged by ash fall. The volcano, and its crater lake, 'Segara Anak' (child of the sea), are protected by the Gunung Rinjani National Park established in 1997.
The highlands of Lombok are forest clad and mostly undeveloped. The lowlands are highly cultivated. Rice, soybeans, coffee, tobacco, cotton, cinnamon, cacao, cloves, cassava, corn, coconuts, copra, bananas and vanilla are the major crops grown in the fertile soils of the island. The southern part of the island is fertile but drier, especially toward the southern coastline.
The water supply in Lombok is stressed and this places strain upon both the water supply of the provincial capital, Mataram, and the island in general. The southern and central areas are reported to be the most critically affected. West Nusa Tenggara province in general is threatened
