Question

How is it possible to grow moderate-climate-type crops such as wheat, barley, and potatoes at an elevation of 4103 \(\mathrm{m}(13,460 \mathrm{ft})\) near La Paz, Bolivia, so near the equator?

Short answer

Moderate-climate crops can be grown at high altitudes near the equator due to the lapse rate phenomenon, which results in lower temperatures at high altitudes. When combined with the steady sun exposure of equatorial regions, this creates an ideal environment for these types of crops.

Step-by-step solution

Understanding the Climate in High Altitudes

In general, the temperature decreases with increasing altitude. This phenomenon, called the lapse rate, says that the temperature decreases by about 6.5 degrees Celsius for every 1000 meters (or 3.5 degrees Fahrenheit for every 1000 feet) you go up. So even though La Paz is near the equator, its high altitude makes its climate suitable for growing moderate-climate crops.

Understanding the Climatic Conditions at the Equator

At the equator, the temperature is typically high due to the direct overhead sun throughout the year. However, this primarily affects regions at low altitudes. It is less significant in regions like La Paz, Bolivia because its high altitude significantly cools the temperature.

Combining the Effects of Altitude and Latitude

Because of its high altitude, the climate of La Paz is cooler than the typical equatorial climate. This combines with the effects of being near the equator, where the amount of sunlight is consistent throughout the year, providing suitable conditions for growing moderate-climate crops like wheat, barley, and potatoes.

Key concepts

Climatic conditions at high altitudes

At higher altitudes, like the lofty heights of 4103 meters in La Paz, Bolivia, the climatic conditions undergo significant transformation. Typically, as you ascend to higher elevations, the atmosphere becomes thinner, leading to cooler temperatures. This can seem surprising given that La Paz is near the equator, a region often associated with heat. However, the cooling effect of high altitudes prevails over the equatorial heat.

Several factors contribute to this cooling:

• Decreased atmospheric pressure: At higher elevations, the air pressure drops, leading to a decrease in temperature.
• Less absorption of solar radiation: Despite the higher exposure to the sun, the thinner air at such altitudes absorbs less radiation, keeping temperatures lower.

These conditions make La Paz's environment suitable for moderate-climate crops like wheat, barley, and potatoes, which require cooler growing conditions.

Lapse rate effect

The lapse rate is a crucial concept in understanding how temperature changes with altitude. In meteorology, it refers to the rate at which air temperature decreases as elevation increases. Generally, the lapse rate is about 6.5 degrees Celsius per 1000 meters or 3.5 degrees Fahrenheit per 1000 feet.

This principle explains how locations like La Paz, Bolivia, despite being near the equator, have cooler climates. As you move up from sea level to higher altitudes:

• Temperature drops steadily.
• There is a shift in climate from warmer to cooler conditions.

Thus, even tropical regions can experience temperate climates at higher elevations due to the lapse rate effect, enabling them to support moderate-climate agriculture.

Latitude influence on climate

Latitude plays a significant role in determining climate. The equator is known for its consistent, year-round high temperatures because of the direct overhead sun. However, this is not the sole factor influencing climate. In regions like La Paz, Bolivia, high altitude moderates the traditional equatorial heat.

How latitude affects climate:

• Proximity to the equator usually means higher temperatures and consistent daylight.
• However, altitude can counteract the heat typically found at equatorial latitudes.
• Both factors create a unique microclimate in places like La Paz, blending equatorial influences with the cooling effects of high elevation.

Thus, the combination of equatorial closeness and significant altitude allows for agriculture that typically prefers cooler environments.

Agriculture in equatorial regions

Equatorial regions, with their rich biodiversity and ample sunlight, offer unique agricultural opportunities. However, farming in these zones often focuses on crops that thrive in heat. In the case of La Paz, Bolivia, the high altitude creates a distinctive setting perfect for growing crops such as wheat, barley, and potatoes, which flourish in more moderate conditions.

Factors contributing to agriculture in equatorial highlands:

• Cooler temperatures from high altitudes improve yield potential for certain crops.
• The consistent daylight length due to equatorial positioning aids in balanced crop growth.
• Microclimates, formed by the interaction of altitude and latitude, provide diverse growing conditions.

Thus, high-altitude equatorial regions like La Paz can defy norms by supporting crops typical of temperate climates, leveraging the cooling altitude factor and constant equatorial sunlight.