The Impact of climate change on Soybean production and farming systems in Western BrazilWith the world population on the rise and the impacts of climate change set to become more prevalent, it has become of crucial importance to study the impacts of climate changes on crop yields. Tropical areas especially can be quite vulnerable to climate change. In Brazil, agriculture is such an important industry as they are one of the largest exporters of a range of arable goods, with agriculture accounting for over 30% of GDP (Marengo et al., 2010). Since Brazil is a large country, the impacts of climate change are likely to vary among the regions. Therefore, the focus of this essay will be on the Western regions (such as Mato Grosso, Western Amazonia) as it’s predicted that these areas are likely to be quite affected under a 2080 temperature & precipitation A2 scenario. Also, an emphasis will be placed on the effects on soybean crops, which is arguably one of Brazil’s most valuable crops and hence yield changes in this crop are likely to impose a very high economic impact on Brazilian agribusiness.

In order to tackle these issues, it is necessary to establish climate change estimates for the worst case scenarios, as to aid farmers with adaptive solutions in order to help sustain crop yields under any situation.

Future projected climate changes

Average temperatures

Figure 1: Change in average annual temperature by 2100 (A2 business as usual scenario) (Meteorological Office, 2012)

Figure 2 – Percentage change in average annual precipitation by 2100 (A2 business as usual scenario) (Meteorological Office, 2012)

Figure 1 shows that average temperatures are set to increase by at least 3.5oc throughout Brazil, with increases of 3.5-4oc likely to hit the western areas of Brazil. However, precipitation models in Figure 2 suggest that there is uncertainty over precipitation changes in 2100 as estimates range from -10 to 10% throughout the region. These maps from the MET office were useful as they combined several models together in an attempt to get a reliable estimate, the sizes of the squares in the key reflects the agreement on values between the models studied.

Temperature variability

Figure 3 – Temperature projections for 2080-2100 (A2 business as usual scenario) (Marengo, 2009)

Figure 4 – Precipitation projections for 2090-2100 (A2 business as usual scenario) (Marengo, 2009)

Figure 3 demonstrates that predict that at a minimum, temperature changes are 2-3 oC, throughout most of Brazil, whereas increases of 3-4 oC can be expected in the north and 4-6

oC in the North West, which would have detrimental impacts on crop yields.

Figure 4 is a major contrast from Figure 2 as it shows that precipitation changes by 2080 are likely to be severe, with the North Western areas set to experience rainfall reductions at a minimum of -20% and a maximum of -40%.

Seasonal Changes

Consequently, the above temperature changes imply that the frequency of frost free days would rise (Marengo et al., 2010), which would present ideal conditions for crops as icy conditions can be lethal for certain crops.

The periods of warm and dry days are also expected to increase during autumn and winter, also ‘Veranicos’ (warm and dry days during autumn & winter) along with the occurrence of dry spells lasting more than two weeks are likely to increase in the future (Marengo et al., 2010). This could result in implications for crop yields as there would be an increased demand for irrigation.

Extreme Weather Events

Table 1: Expected extreme weather events by 2080 (Marengo et al., 2010)

Climatic change ImpactsHeatwaves The number of days above 32oc would

increaseStrong Winds Could make spraying of pesticides difficultDrought Risk Severe for crop yieldsHumidity As a result of rises in temperature and

water vapour, this could increase the occurrence of diseases in Soybean crops

Agricultural Impacts

Brazil currently operates a No-tilling farming system and multiple cropping where soybean and maize are grown together (Brazil Ministry of Agriculture, 2015), which is very effective as it reduces the influence from erosion and ensures that the soils are resilient and sustain fertility. They also have a useful role in sequestering carbon (Ogle et al., 2012).

Table 2: Importance of crops by harvested area, Quantity and Value (FAO, 2008)

Table 2 shows an overview of that the most valuable crops produced in Brazil, where soybeans are listed as one of the most valuable crops produced, with an estimated value of $12.8 billion in 2008.

Table 3: Crop Yield Impacts Overview (Marengo et al., 2010)

Table 3 shows the predicted impacts on individual crops based on available potential area under different A2 scenarios, and upon observation, soybean is shown as the most affected crop in the future as it experiences the highest losses in areas from now to 2080 under a business as usual scenario.

Figure 5: Key agricultural commodities in the Brazilian regions by planted area (Strohm et al., 2012)

Figure 5 shows the importance of soybean across Brazil, where the focus will be on the impacts on Western areas such as Mato Grosso, where soybean accounts for over 60% of the total planted area.

Table 4: Estimate of soybean impacts in Mato Grosso (Zullo et al., 2008)

The main impacts of concern are an increased incidence of heat stress, where high temperatures would be detrimental to soybean yields, where the optimal temperature for soybeans is predicted to be approximately 23oC (Hatfield et al., 2011). Table 4 is alarming as it shows the impacts of different temperature increases on soybean yield, and this can have huge implications on farming in the Mato Grosso, where Figure 5 had highlighted soybean as the main produce, as a temperature increase of 3oc was studied by Zullo et al. (2008) to vastly reduce the suitable area available for soybean, along with huge economic implications for the region, which illustrates the necessity for adopting adaptation strategies to counteract these consequences.

In Western Amazonia, as well as parts of the Mato Grosso, the changing of land use from forest to soybean is set to adversely affect the water balance, which would have an impact on the local climate (Magrin et al., 2014). This would reduce the availability of water for irrigation and could affect water resources in the area. This suggests the water needs of

soybean is set to rise significantly by 2080, coupled with the decrease in precipitation and therefore measures to sustain water may be crucial for the Western regions of Brazil.

Soybean rusts are also predicted to become prevalent by 2080 (Magrin et al., 2014), whereby the predicted rises in temperature and humidity are strongly linked to plant disease as seen from climatic models (Alves et al., 2011).

It’s also important to note that soybean cultivation itself is contributing to climate change in the western regions, since deforestation would result in a rise in temperature and a fall in precipitation, especially in the dry seasons (Sampaio et al., 2007). It’s expected that this clearing of land for cultivation will increase in future, therefore actions would need to be taken to sustain soybean yields.

Adaptation Strategies As the current population rate is set to vastly increase in the future to 2050, global soybean yield would need to increase by 140% to accommodate the world population (Bruinsma, 2009). Therefore, this is quite crucial for Brazil due to its reputation as the second largest soybean producing nation. In order to battle to sustain soybean yields in Western Brazil, a variety of adaptation measures are needed.

Water Use Efficiency

Improving water use efficiency would be necessary to implement pre-2080, in order to be prepared for the predicted reduction in precipitation by a vast 20-40% in Western Brazil, as shown in Figure 4. To achieve this, it’s necessary to promote techniques and cropping systems of higher water use efficiency.

Firstly, it would be advisable to install sub surface drip irrigation on the soybean-Maize cropped plots, as it is very water efficient in decreasing water demand and irrigation costs to farmer (Levidow et al., 2014). These are drip lines which maintain irrigation for different field lengths and helps leave space in the soil to store water from rainfall (Payero et al., 2005). This technique works by ensuring water is irrigated through the crop, rather than on the soil surface to reduce evaporation loss (Condon et al., 2004). This may be quite expensive investment to install, though money would be saved in the long run, since in order for Brazil to try and sustain their soybean yield nutrients, as shown in Table 4 where there would be high financial constraints for a loss of yield.

Crop resistant cultivars

It would also be useful to invest in adapting new soybean crop varieties that are resistant to future conditions such as heat stress, drought and diseases. Drought tolerant cultivators adapted to future conditions is a useful option, as Sadok & Sinclair (2011) imply that taking advantage of a genotype that helps reduce transpiration on the surface of the leaf and would help conserve soil water.

Developing Soybean crop varieties adapted to higher temperature is necessary as soybean optimal temperatures were studied to be around 23-24oC, where temperatures above this range reduce yields with no yield at 39oC (Hatfield et al., 2011). Heat tolerance from new crop variations should help farmers cope with future heatwaves that are predicted to increase in duration (Table 1).

Pests and Disease prevention

Since climate change has a large influence on insect pest and pathogen outbreaks, this would certainly be the case for Western Brazil (Sutherst et al., 2011), and would need to be tackled in order to sustain soybean yields.

Integrated Pest Management (IPM) would be a good approach to follow, especially as Brazil are ranked as one of the largest consumers of pesticides worldwide also since phytophagous arthropods have been known reduce soybean productivity (Bueno et al.,2011). This focuses on preventing pest influence through a range of methods such as through the use of resistant cultivators, it also has the advantage of being economical and environmentally friendly and is compatible with soil tillage, nutrient supply and water management (Juroszek & Tiedemann, 2011).

Soybean could be at a higher risk of soil borne diseases (Vries et al., 2010), therefore Cultivar breeding (Juroszek & Tiedemann, 2011) would be necessary to ensure that crops are adapted to any disease since relative humidity and temperature is predicted to increase in the future in Western Brazil.

Farm management practices

Crop rationing would be a useful practice to consider, to ensure that the water balance stays stable by decreasing soybean’s water demand to aid in water conservation (Debaeke & Aboudrare, 2004), this would especially be useful during veranico periods and to minimise the destructive impacts of land clearance for soybean cultivation in areas such as Western Amazonia.

Soil management practices such as conservation tillage would be useful to manage soil fertility and reduce evaporation loss on the soil surface (Levidow et al., 2014). Conservation tillage helps to maintain both soil fertility and the soil’s ability to hold water through measures such as scheduling of irrigation at night to lower evaporation (Levidow et al., 2014).

Making use of crop rotations would be helpful in decreasing the risk of disease in soybean, the rotations would weaken pathogens that inflict soil borne diseases (Strand, 2000).

In addition, the planting dates of soybean would need to be modified to help sustain high soybean yields, as Travasso et al. (2008) observed improved productivity in regions of Uruguay and Argentina. Therefore, sowing soybean crops earlier the summer can prove beneficial to sustaining yields in the future.

ConclusionsClimate change in Western Brazil is likely to result in temperature increases of approximately 3-4oc and an annual precipitation decrease of up to 40% by 2080 under a business as usual scenario. This would also result in extreme weather events such as heatwaves, drought and an increase in humidity which would have drastic effects on soybean yields. This is a huge concern for Brazil as soybean yield reductions would have a heavy economic impact on Brazil’s agri-business sector and farmer’s income, especially in regions such as Mato Grosso where soybean is the main crop. Adaptation strategies are essential for Western Brazil, notably as land clearance for soybean would alter the local climate further. Sustainable farm management practices, alongside strategies such as improved water use efficiency, developing crop resistant cultivars and a controlled pest management system would prove a worthwhile invest and can counteract the projected yield declines predicted from a worst case climate scenario.

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