干旱区生态环境知识资源中心

The present review accounts for the most important climatic data published until 1992 about Venezuela, and attempts to correlate them with other results from tropical South America. The evidence of climatic changes prior to the Last Glacial Maximum consists of several terrace levels, one of which representing an arid oscillation dated isotopic stage 6. Older terraces have not been dated and their meaning still remains questioned. The Late Merida Glaciation Stage began between 19 and 16 ka, and ended around 13 ka, associated with an arid or semi-arid climate in the lowlands. The Post Glacial times (after 13 ka) were characterized by oscillations of colder and warmer climates in the mountains, correlated respectively with drier and wetter ones in the lowlands. The early Holocene is characterized by a climate similar to the present-day one, followed by a colder and drier phase around 6 ka. Present-like conditions established again until about 3 ka, when a new warm, humid phase began with a maximum at 2.5 ka. Later on, the current climate dominated. However, some minor oscillations occurred, the most notable one in the Little Ice Age (14th to 19th centuries). These climatic trends agree with those reported for the majority of the South American tropical regions, but a certain degree of heterogeneity exists in the Holocene, attributed to differences in the local climatic patterns and or to the high frequency of changes, the intensity and duration of climatic oscillations, as well as to differences in biotic responses conditioned by the internal properties of the ecological systems.