The effects of changing climate-drought and desertification
We cannot command Nature except by obeying her.
— Francis Bacon
Drought is a temporary weather condition resulting from a shortage of rainfall which reduces water availability below normal. One short-term consequence of drought is loss of groundcover plants. Desertification results when warmer temperatures lead to a more permanent loss of soil moisture.
During periods of normal soil moisture, as outdoor daytime temperatures go up the humidity begins to drop. This results in a quickening of the evaporation rate of moisture from the soil. When temperatures drop at night the outdoor humidity level can rise until the temperature stops dropping or the dew point is reached. Once the dew point is reached the moisture condenses and is added back to the soil in the form of droplets of rain or dew. If the temperature drops below freezing the water is added back to the surface of the ground by the deposition of snow or frost which can return the moisture to the soil as it melts. cooling. Most building materials have some moisture-holding capacity; this helps to balance the short-term effects of drought as they give off some of their moisture to the interior of the building.
According to Tim Flannery in The Weather Makers: “The potential of climate change to spawn drought almost anywhere on the planet is so great that leading climatologists have recently warned that ‘it would be a mistake to assume any region is safe from megadrought.’ In this regard, it is worth pointing out that the near record rains the United States experienced over the winter of 2005 in parts of the southwest were not sufficient to make up for the preceding dry years, while the northwest remains in the grip of unprecedented drought” (Flannery).
As more areas begin to suffer from desertification, there will be a corresponding drop in the building materials’ and furnishings’ moisture content. This can result in shrinking and cracking if artificial means of maintaining humidity levels aren’t available. In general, wood materials will tend to shrink when the humidity is low and expand when the humidity is elevated. Most of the movement occurs along the width and depth of the wood with very little change in the length. Most materials are installed in ways that tend to help minimize the adverse effects of these movements. For a two-by-four wood stud the change in dimension isn’t apparent since the length doesn’t change much and the movement of the width and breadth is generally hidden by the wall, the floor and the ceiling coverings. The movement is much more obvious on materials where all the grain tends to run the same direction such as wood floors. Floors don’t shrink or swell much along the length of the wood, but can vary dramatically across the width.
Until the climate stabilizes, fluctuations in humidity can be expected to go through cycles of increase and decrease. Many of the changes that can occur from shrinking are cosmetic and will show up as cracks or widening gaps at the floor joints. This is the most common scenario when a climate becomes drier. When a building is built in dry climates, and the climate shifts toward higher humidity, the materials must have the necessary room to expand. If the necessary expansion joints or gaps aren’t present the floors may buckle when they run out of room. If this is recognized early, the use of dehumidification equipment may be sufficient to dry the floor and allow it to shrink and settle back into position.
What You Can Do
- Follow the manufacturer’s recommendations to allow for shrinkage and expansion when installing building materials.
- Consider using wider baseboards to hide greater expansion and contraction at the edges of wood floors.
- Purchase a temperature/humidity gauge for monitoring the indoor and outdoor humidity levels. Short-term indoor humidity fluctuations shouldn’t be a problem, but watch out for high or low humidity extremes that don’t resolve themselves in a few hours.
- Use dehumidification to reduce the humidity if floors swell and begin to buckle.
- Add humidity if floors shrink and crack.
- Be cautious of humidifiers installed in the ventilation system. These may be difficult to maintain and may encourage bacterial and mold growth.
- Consider adding plants or water fountains if the humidity levels are low. Make sure to monitor to keep moisture levels ideally between 30 and 50 percent and above 60 percent for only short periods of time.