They go largely unobserved and unattended. In view of the climate change that is with us today, this is a huge missed opportunity: microclimates.
As long ago as 1949, Wolfe, Wareham and Scofield, in a meticulous description of the microclimate in the small Neotoma valley in Central Ohio, observed there is much attention for predictions and trends of macroclimate, but far less understanding of how this translates in weather at a local level.
The same holds true 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 in time and space in less understood.
What is a microclimate?
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 and 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 seasons, moisture retention - determine, the moisture available to the 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 effect of microclimates may either buffer against climate change or may amplify its effects, be it temperature peaks, droughts, irregular or late rainfall. See the mosaic of interactions on the right.
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 the larger climate change.
How are microclimates managed?
The first important intervention is to improve water retention at a landscape level by water harvesting, by water spreading and by erosion and drainage control. 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 regreening. Vegetation 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 others. Vegetation canopy can retain moisture. The presence of small forests in an open landscape can create local winds.
A good example is the Tigray and Amhara regions in Ethiopia, where intense development of the landscape caused much change: shallow groundwater tables have come up, moisture has been secured and vegetation boosted – all these having a tremendous impact on the local climate. Agricultural productivity rose not only as an effect of secured moisture but probably also as an effect of gentler microclimates and higher soil nitrogen availability.
Microclimates at a landscape level
Understanding the microclimate is an essential part of managing an ecosystem. It is also a call for intensive change – instead of isolated interventions, managing microclimates rests on a critical sum of measures that creates a systematic change of microclimates at landscape level.
Moreover, there are different conceivable strategies in intensive watershed management and regreening – the method of water harvesting practiced (run-off storage or water spreading) or the type of vegetation promoted – all having a different impact on the microclimate.
The management of microclimate is a powerful frontier, but not well understood, to smoothen out the impacts of climate change and at the same time create more resilience through more stable agricultural ecosystems.
We are reviewing microclimates in a project entitled ‘Harnessing Flood for Better Livelihoods and Ecosystem Services'. As part of the review, we are exploring questions such as: does the capture of run-off in different parts of the landscape – upstream, midstream or downstream – have an effect on the microclimate? If so, where is the largest impact? Also, can we optimize it and make better use of it?
For instance different ways of capturing and spreading run-off may effect the distribution of soil moisture differently with knock-on effects on soil temperature or on capillary rise. At this stage the challenge is to come to grips with the forgotten factor: the microclimate.
The next step is to position microclimate versus macroclimate change, as was done in Neotoma. The question is: can better management of the microclimate ward off the threats of larger climate change? Or even better – make smarter use of climate change as it comes?
Ecosystem services (including microclimates) in relation to the managed distribution of floodwater and run-off is investigated under the CGIAR Research Program on Water, Land and Ecosystems’ project, Harnessing Floods for Enhanced Livelihoods and Ecosystems Services.