Climate Change

Microclimates unattended

Weather scientists must develop a better understanding of microclimates to protect agricultural ecosystems against climate change

By Frank van Steenbergen
Published: Friday 07 August 2015

They go largely unobserved and unattended. In view of the climate change which affects us today, they are a huge missed opportunity.

But microclimates were meticulously described as long ago as in 1949. Wolfe, Wareham and Scofield, in their book “Microclimates and Macroclimate of Neotoma, a Small Valley in Central Ohio”, had noted that there is much attention for macroclimate predictions and trends, but far less understanding of how this translates into weather at the local level.

Their observation holds true even today. Climate science has a large interest in “average weather”. There is an obsession with predicting larger climate trends: regional long-term patterns of rainfall, temperature peaks and averages. How this pans out locally over time and space is less understood.

Microclimates are the wonderful local interplays between factors such as soil temperature, air temperature, wind directions, soil moisture and air humidity—affected by day-night effects and seasonal effects. They are determined by the particular landscape, soil conditions, vegetation, land use and water retention.

Basically they are where meteorology lands on earth and where a dynamic interaction of forces—local heat exchanges, capillary rise over the year, water retention—determine the moisture available to different ecosystems, the presence of dew and frost, the actual temperatures for plant growth, the vigour of soil biotic life and capacity to fixate nitrogen and the occurrence of pests and diseases.

The effects of microclimate may either provide a buffer against climate change or they may amplify its effects in the form of temperature peaks, droughts, irregular rains or delayed rainfall.

The figure below shows a mosaic of interactions between different factors.

What is more is that microclimates can be influenced and managed. There are several interventions that can affect the microclimate and hence the ability of an area to cope with and even make beneficial use of larger climate change.

The first important intervention is to retain water better at the level of the landscape with water harvesting, water spreading and controlling erosion and drainage. This increases the soil moisture available in a landscape. When there is more moisture in a landscape, it will even out temperature peaks and lows, both in the air and the soil at different depths. It will have an effect on dew formation and the risk of night frost. Moreover, secure soil moisture is a big boost to the ability of soil bacteria to fixate nitrogen and add to the overall fertility of the landscape.

Another intervention is re-greening. Vegetation (like soil moisture) affects how much heat is absorbed in an area and how much is radiated. It affects the circulation of air temperature at different layers and the speed and direction of winds and the movement of dust particles, among other factors. Vegetation canopy can retain moisture. The presence of small forests in an open landscape can create local winds.

A good example are the areas where high density watershed improvements have caused many changes—as in parts of India, Thailand, Ethiopia or Rwanda—where shallow groundwater tables have come up, moisture has been secured and vegetation boosted.  Agricultural productivity jumped not only because of the secured moisture but also due to gentler microclimates and higher soil nitrogen availability.

Understanding the microclimate is an essential part of managing ecosystems. It is also a call for intensive change—not making isolated interventions but having a critical sum of measures that creates a systemic change at landscape level.

Moreover, there are different strategies conceivable in intensive watershed management and re-greening—the type of water harvesting being done (run-off storage or water spreading) or the type of vegetation promoted—all having a different impact on the microclimate.

Though less understood and largely underutilised, the management of microclimate is a powerful tool to smoothen out the impacts of climate change and at the same time create more resilience with more stable agricultural ecosystems.

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