Table of Contents

Introduction

About

Section 1
Natural Foundations of Vilcabamba's Environment
-Geology and Soils
-Climate
-Rivers and Hydrology

Section 2
Human Influences

Section 3
Plant Systems and Species

Acknowledgements

Sources

CLIMATE

General Characteristics

The climate of Vilcabamba is temperate sub-tropical; sometimes proudly referred to by locals as “perpetual spring”. At lower elevations, the temperature ranges between about 13 and 24oC (55 to 75 oF), with an average around 20oC (68oF). In this climate, papaya, banana and chirimoya flourish alongside blackberries (mora) and oranges.

The Rains

The contrast between wet and dry seasons is striking. For example, total monthly rainfall in February is usually around 140 mm (55 inches), while the typical August rainfall is closer to 15 mm (6 inches).

The wet season begins in October or November, but during these months there are still many days with no rainfall. By far, most of the valley’s 800 mm (315 inches) of annual rainfall comes in the months of December through April. In these months, a typical day begins with a sunny, hot morning. Clouds develop in the afternoon, bringing quite heavy rainfall for two hours or more. These afternoon rains are often accompanied by lightning and thunder. Rain can also be more constant over periods of several days; but on the other hand, quite long dry spells during the wet season are also not uncommon.

As a rough guide, Vilcabamba has about 200 rainless days per year; and in the dry season, long stretches of clear skies are typical. The reality, though, is that rain is a possibility at any time of year. A dark storm may brew up on one side of the valley, while the other remains sunny and warm. Hikers are often taken by surprise when a sudden downpour arrives minutes after they have been sweating in the heat of what seemed like a relentless sun.

Climate Shapers

Coastal Influences

Because Vilcabamba lies close to the equator, the amount of heat energy received from the sun does not vary much through the year; so this is not the cause of seasonal differences. Instead, as for most of Ecuador, coastal currents are a key influence on seasonal rainfall.

The Humboldt current brings an upwelling of cold water from a deep ocean trench that runs along the west coast of South America. This current prevails in April/May through October/November, yielding dry weather. During the rest of the year, a southward-flowing warm equatorial current forces the cold water upwelling south of Ecuador. The resulting warm, moist air off the ocean brings rain. At its extreme, this El Niño current has a devastating effect on the coast; and the large thunderstorms that result can disrupt high altitude jet stream winds, causing climatic disturbances over large parts of the planet.

Peru’s Arid Air

Some other parts of the Andes that are at a similar altitude as Vilcabamba are bathed much of the time in coastal cloud; moist air masses carried inland on the easterly winds. But because the coastal plain of northwest Peru is very arid, the air that blows across to Vilcabamba is relatively dry.

An Amazonian Touch

At some times of the year, moist air from the Amazon spills over the eastern flank of the Andes, falling as a heavy mist or fine cold rain called the paramo mist. The mist often results in late afternoon double rainbows, especially in May. Cool air also flows down from higher elevations along canyons and gullies, bringing cooler evening temperatures, and influencing microclimates.

Wet and Dry Season Landscapes

Vilcabamba’s dry season landscape of arid, brown hills -- on which only cactus, acacia and other dry-tolerant plants thrive -- contrasts strongly with the lush greenness of the wet season landscape. Many trees and shrubs lose all or most of their leaves in the dry season. With the rains, the hillsides come alive with grasses, and with the many other varieties of plants, shrubs and trees that spring into action to produce new leaves and flowers. Farmers also time their plantings to take advantage of the rains. Some take the gamble of an early planting, hoping to catch a brief rainy period that often occurs in October.

Mid October (end of dry season)

Mid January (middle of wet season)

Microclimates

Climate of course varies with altitude. At the lower levels in the valley, the mean annual temperature is about 20oC (68oF). At 3000 m (about 10,000 ft), the mean annual temperature is closer to 10 oC (50 oF). Also, the amount of rainfall increases with altitude, at least up to 2500 m (about 8000 ft).

Microclimates within the valley are also created by differences in landform (topography), and type of vegetation. Within quite small areas, temperature, wind patterns, and humidity can differ fairly dramatically from those of the surroundings. For example, hillside gullies are often considerably cooler and more humid than the surrounding slopes. There is more information on the environment of the gullies in Section 3 of this booklet.

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