Introduction

The dry forest and scrub vegetation in Brazil, generally called ‘caatinga’, covers an estimated area of 6–9 × 105 km2 in the northeastern region. It is conditioned by the prevailing semiarid climate, with high potential evapotranspiration throughout the year (1500–2000 mm y−1) and low rainfall (300–1000 mm y−1), which is usually concentrated in 3–5 months and is very erratic (Reddy, 1983). Drought years are common and severe droughts lasting 3–5 years have occurred every 3–4 decades.

The area has been inhabited for more than 10,000 years, mainly in the river valleys and humid mountains, but according to early colonial sources, population density was generally low. Cattle raising spread in the 18th century and still is the main economic activity. From that period on, population pressure has increased in more favorable areas, where subsistence agriculture is practised in fenced plots. Until the middle of this century, cattle roamed freely on the non-agricultural land, independently of land ownership, but most properties are now fenced.

Land productivity is low and since resources are limited and birth rates have been high, the area has been a center of continuous migration to more favorable places in the same region, mainly the coastal area, or to other regions in the country. Migration increases during catastrophic drought periods. Nonetheless, population has steadily increased in the area and most of it has remained at a bare subsistence level. Social and economic parameters are the worst in the country, from lowest per capita income to highest illiteracy.

Government efforts to foster economic development in the region have centered on the coastal area, except for large irrigation projects.