By Dr. Rodrigo Cazanga, head of agricultural production and weather at Chile's Natural Resources Information Center (CIREN)

Since the Neolithic agricultural revolution man has interferred directly with the carbon dioxide content of the atmosphere, but it has only been since the industrial revolution that this interference has been markedly noticed. The trend of global warming has increased through the 20th and 21st centuries.

Today it is estimated that through the burning of coal, oil and other fossil fuels, as well as deforestation, the carbon dioxide content in the atmosphere has risen 25%, which generates an overall warming trend in the troposphere producing a greenhouse effect.

According to the Intergovernmental Panel on Climate Change (IPCC), a doubling in greenhouse gases would raise the global temperature between 1-3.5°C in 100 years.

While it may not seem like much, this is equivalente to going back to the last ice age but in the opposite direction. On the other hand, the rise in temperature would be the fastest in the last 100,000 years, making it very difficult for the world's ecosystems to adapt. Other predictions are even more catastrophic, expecting the global average surface temperature to rise by around 3°C in the next 50 years, due to the increase in emissions from carbon dioxide and other gases.

The climate change that is expected in the coming decades could have as a consequence a decline in agricultural yields and the available irrigation water for some regions. In this way, agricultural lands would be converted into deserts and in general there would be big changes in terrestrial ecoysytems.

With this background, it is important and convenient to evaluate the effect of probable future climatic conditions and the concentration of carbon dioxide on the productivity of crops, to design and implement adaptation programs.

Figure 1

With the object of evaluating the effect of climate change on the production of blueberries, an agroclimatic zoning of productive aptitude was conducted in the region of Maule. For its part, we coudl say that a zoning of productive aptitutde is a powerful assistance tool for making decisions about fruit investment or restructuring.

This is because it makes a map available that indicates the areas that are more or less suitable for a particular plant species and/or variety, which is very useful for the grower or investor to focus their investment, reducing costs and risks (figure 1). For this preliminary example, the zoning considers thermal parameters (heat summation, chill hours, hourly temperatures, frost-free periods, daily maximum and minimum temperatures).

These parameters are calculated for current and future climates. The productive aptitude is estimated by taking into account the productive requirementes of the Brigitta variety with the prevailing climatic conditions through an ecophysiological model. Productive aptitude values were summarized into five categories: 1) without (dark green), 2) mild (light green), 3) moderate (yellow), 4) severe (brown), 5) exclusive (red).

Figure 2

Current climatic conditions were calculated and spatialized considering the historic records of weather stations, the regional orography and thermal satellite images. In the case of the future climate, data was used for an 'A2' scenario (medium-high emissions) that the geophysics department at the Universidad de Chile has available. What the results show for Brigitta is that there would be a reduction in land surface for category 1, with the regional surface area declining from 36% to 19% between the current and future thermal conditions.

For the same variety, the surface area of category 2 would rise, going from 10% to 45% (figures 1 and 2).

In addition to surface area changes for every category of aptitude, variations would also occur in the geographical distribution of such areas. This study is part of the activities of the project "Generation of digital media to improve competitiveness in the production of blueberries in the Maule Region" from Innova-CORFO, CIREN, executed by the University of Talca.

According to the results and taking into account the climatic conditiosn defined under scenario A2, we can conclude that:

1) In the Maule region, the surface area with better climatic thermal conditions for production of Brigitta blueberries will be reduced.

2) Breeding programs to adapt to climate change should develop varieties whose metabolism by a broader thermal range and top end cardinal temperatures that are greater than current ones.

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