Relief, drainage, and soils

The Dominican Republic includes the highest and lowest elevations in the West Indies. Its major mountain ranges and elongated, fertile valleys mainly extend from northwest to southeast.

The Cordillera Septentrional, the northernmost range, looms above a narrow coastal plain drained by such short rivers as the Balabonico and the Yasica. The southern slopes of the mountains give way to the extensive Cibao Valley, which stretches from Manzanillo Bay in the northwest to the Samaná Peninsula and the Bay of Samaná in the east. The valley’s fertile soils are fed by two of the nation’s main river systems: the Yaque del Norte, which flows generally northwestward, and the Camu-Yuna system, which flows eastward.

The Cordillera Central, the island’s most rugged and imposing feature, is known in Haiti as the Massif du Nord (“Northern Massif”). In Dominican territory its crest line averages some 6,000 feet (1,800 metres) in elevation and rises to 10,417 feet (3,175 metres) at Duarte Peak, the highest mountain in the Caribbean. Other prominent peaks are Yaque, La Rucilla, Bandera, and Mijo. Tributaries of the Yaque del Norte drain most of the range’s northern flanks, whereas its southern flanks are drained by the Yaque del Sur system and the Ocoa, Nizao, and other smaller rivers. The San Juan River, one of the Yaque del Sur’s main tributaries, is the centrepiece of the fertile San Juan Valley, which connects with Haiti’s Central Plateau via the upper Artibonite River valley.

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Bounding the San Juan Valley to the south is the Sierra de Neiba, which corresponds to the Matheux and Trou d’Eau mountains of Haiti; its high peaks reach approximately 7,200 feet (2,200 metres). Water flowing off the Neiba range drains partly to the Caribbean, via the Yaque del Sur system, and partly inland, to saline Lake Enriquillo. Enriquillo is the country’s largest natural lake, about 23 miles (37 km) long and up to 11 miles (18 km) wide; the lake’s surface is also the lowest point in the West Indies, at 144 feet (44 metres) below sea level. The Dominican Republic’s southernmost range, the Sierra de Baoruco (Bahoruco), is called the Massif de la Selle in Haiti; it overlooks Cape Beata and the arid southwestern plain, including the largely infertile Pedernales region.

The Cordillera Oriental forms the country’s less-rugged eastern spine, separating a narrow coastal plain to the north from a wider belt of rolling lowlands to the south, where most of the country’s sugarcane is grown. The region’s main rivers all flow to the Caribbean, including the Ozama, which reaches the coast at Santo Domingo, and the Macorís, Soco, Chavón, and Yuma.

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The country’s most fertile alluvial soils are located in the valleys of the Yaque del Norte, Yuna, San Juan, and Yaque del Sur rivers, as well as the Ozama and various smaller rivers in the southeast. The mountain slopes have lower-quality soils and are generally covered in forests and grasslands. Salt deposited around Lake Enriquillo creates some of the nation’s only unproductive soils.

Climate

The Dominican Republic has a moderate, relatively mild tropical climate, although it lies well within the tropical zone. Conditions are ameliorated in many areas by elevation and by the northeast trade winds, which blow steadily from the Atlantic all year long. The annual mean temperature is 77 °F (25 °C); regional mean temperatures range from 69 °F (21 °C) in the heart of the Cordillera Central to as high as 82 °F (28 °C) on the coastal plains. Temperatures rarely rise above 90 °F (32 °C), and freezing temperatures are unknown.

The heaviest precipitation is in the mountainous northeast (the windward side of the island), where the average annual rainfall is more than 100 inches (2,540 mm). As the trade winds pass over the country, they lose their moisture on various mountain slopes, so that the far western and southwestern valleys, along the Haitian border, remain relatively dry, with less than 30 inches (760 mm) of annual precipitation. The northwestern and southeastern extremes of the country are also arid. The Dominican Republic is occasionally damaged by tropical storms and hurricanes, which originate in the mid-Atlantic and southeastern Caribbean from August until October each year; hurricanes in 1930, 1954, 1979, and 1998 were particularly devastating.

Plant and animal life

Vegetation varies considerably, but there is generally more ground cover in the Dominican Republic than in neighbouring Haiti. The mountains are still largely forested with pines and tropical hardwoods, although the trees on the lower and more accessible slopes have been severely cut for use as charcoal and commercial lumber. In the drier regions low shrubs and scrub predominate, but grasslands and dense rainforests occur where there is heavier precipitation. Royal palms grow throughout much of the country. Cultivated crops have largely replaced the natural vegetation in many areas, particularly in the more fertile upland valleys and on the lower mountain slopes. Mangrove swamps line some coastal areas, whereas extensive sandy beaches are found elsewhere, notably along the northern shore.

Wild animals are not abundant; for several centuries cattle and goats, introduced by the early Spanish colonists, ran wild on the grasslands and in the desert areas. Alligators are found near the mouths of the Yaque rivers and in the waters of Lake Enriquillo. A great variety of birds, including ducks, are hunted. Fish and shellfish inhabit the surrounding waters, particularly within the coral reefs.