Although these forests are presently reduced to a few small stretches of coastal environment, the presence of floristic elements related to the semiarid northeast of Brazil (caatinga) and to southern South America (chaco) leads to the conclusion that this vegetation occupied much more extensive areas in the past, probably during the well documented cold, dry climates of the Quaternary period. Ab’Sáber (1974) has postulated that in the last dry period of the Quaternary (18,000 – 12,000 years B.P.), the caatinga covered a much larger area than it does today. The southern arm of this vegetation must have stretched to São Paulo and south-central Minas Gerais. During the same period, the semiarid vegetation types from the dry regions of Argentina extended up the coast through Uruguay and Rio Grande do Sul to southern Bahia, along the then widened coastal region associated with lower sea levesl (figure 9). The distribution of the genus Caesalpinia also seems to support this hypothesis for its approximately 150 species are mainly found in drier or semi-desertlike, tropical and sub-tropical regions. In South America, around 90% of the species of this genus demonstrate this preference.
During the dry periods of the Quaternary, the Atlantic coastal forests of eastern Brazil became restricted to several small refugia, the location of which is hotly debated. These refugia expanded once again when wetter condition returned. Several studies show that these changes in climate were cyclical and considerably influenced plant and animal distribution (Bigarella & Andrade-Lima, 1982). Therefore it seems safe to assume that the inicial stock of pernambuco wood became established and spred out during these cold, dry periods. It was most likely distributed over a large part of the expanded coastal regions of those periods. However, with the return of the hot, humid climate which reigns today, the distribution of pernambuco wood became restricted to a few sites along the coast where condition similar to those of drier paleoclimatic periods have prevailed. Within these enclaves, relict populations of Caesalpinia echinata, resistent to changes in climate, have survived in isolation, separated by stretches of more humid forests. This has been observed in Rio de Janeiro, Bahia and other areas of northeastern Brazil.
Areas where remnant populations of this species have been found in the last 10 years are located in the following Brazilian states: Rio Grande do Norte, Paraiba, Pernambuco, Alagoas, Bahia, Espirito Santo, Rio de Janeiro and São Paulo.