Every site has different places on it that can have different temperatures, levels of shade, and other variables. These are caused by sun direction, topography, water bodies, built structures and vegetation. You can enhance your ability to recognize these microclimates and also where there are opportunities to create or enhance them by understanding them and through observation.

These can be a key part of the decision making process on where you place plants and living spaces. Any site can and usually does have multiple microclimates. You can also create microclimates with your design. We share a number of examples of how to do this below.

An aspect of a site is the compass direction a slope is facing. The direction a slope faces can create different temperatures, moisture levels, sunlight levels, and other variables. This can affect what you can grow on that site to a great degree, as well as your comfort. These microclimates can also be affected by sun angle (caused by season or latitude), slope steepness, water bodies, built structures and vegetation. You can increase your ability to recognize these microclimates and also where there are opportunities to create or enhance them by understanding what causes microclimates and through observation.

Microclimates can be a key part of the decision making process on where you place plants and living spaces. Any site can and usually does have multiple microclimates. You can also create them with your design. We share a number of examples of how to do this below.

Effects_of_aspect_on_vegetation-_SW_Idaho

By Thayne Tuason - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=32519981 here

Pine trees grow on north slopes in many drylands because prevailing winds drop more snow and moisture, and it melts off more slowly, allowing more absorption into the soil. South facing slopes are hotter and drier and support only desert or drylands plants.

In cooler climates, stone fruit trees can benefit from being on the north side of slopes because the cold can delay fruiting. On the east side of slopes, flowers and fruit can be damaged by late frost when the sun hits them early. On the other hand, in warmer climates, south slopes are preferred as that extra warmth can prevent frost damage to roots or other vulnerable areas, especially if there is water or other elements that can hold the heat gathered from the sun and release it at night.

On the other hand, you may have less water and more drying on the southern and especially western slopes because of the sun and heat effect, so you’ll need to do more to ensure the soil stays moist by addressing some of the other aspects of microclimates.

An exception to this dry western slope is found in the mountain ranges of the Pacific coast of the US. The moisture coming from the ocean on the west tends to stay on the western slopes, and the eastern slopes are much drier. This dry effect, where very tall mountains prevent rain from moving east, lasts for hundreds of miles over some of the largest deserts in the US. In this case, the influence of the ocean is stronger than the sun.

The direction of the slope is an important factor in determining the suitability of land for different crops or other uses.

These rules are not hard and fast - there are a number of factors that impact aspects, like steepness of slope, overall moisture level and wind. The aspect of the slope can determine many things about what you can do on that slope, so be sure to check out your local region to find out how the slope aspect works in that region. This is an important factor in what I look at when making land purchase decisions, especially in hilly or mountainous areas. Can I grow what I want to grow on the slope of the land I’m looking at? Does the land offer several aspects, thus, different microclimates?

It’s important to consider the effect of the sun aspect on housing. A house on a northern slope in a colder climate will be much harder to keep warm and have much less light than one on any other slope. In his book, Collapse, Jared Diamond posits that the reason Vikings were unable to survive on Greenland while indigenous populations thrived even further north is because of microclimate choices. One can note that many northern cities are placed on slopes that have some southern influence.

In the tropics, the sun aspect doesn’t change much during the year. Aspect might influence how hurricanes might impact you, or where the cooling breezes reach. Many homes in tropical settings are built on slopes that face the ocean in order to capture the cooling breezes that almost constantly flow there. This opens them to hurricane damage, so that must be considered too. Here is one version of a home near the shore protected from hurricanes.

Mollison.

There are a couple of things to consider here. This property is well protected and would likely survive even a Category 5. There are some sacrifices too - the air flow so important to passive cooling in the tropics is not so readily available, Also, in a hurricane, storm surge or flooding might be a real problem for this house depending on its altitude, the watershed, and where exactly it’s located. Flooding can be a major issue even with relatively minor tropical storms and is something to pay close attention to, when siting buildings or other permanent elements.

The way a house is set is also key in relation to aspect. Most of the time, houses should be set with the south and north sides being the long side. This is because in hotter zones, this minimizes the square footage of a house that is warmed up in the AM and baked in the afternoon (east and west) in summer when the sun is high. East and west exposure can heat up the house even more than southern exposure. Developers almost never think about things like this.

In temperate climates, you generally want more sun exposure in the winter and a wide southern exposure is ideal for that as the sun is in the south the entire day in winter.

Check Your Understanding

3.2.2. Microclimates – Aspect

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