Crop Models: A basic introduction

Crop models have 'cropped' up a few times in my previous posts. Mathews et al., (2007) highlighted the importance of incorporating crop models when considering agricultural policy. This factor has resulted in a boom in crop modelling studies throughout academia and, therefore, provides a great focus for my blog over the next few months.

So if you know me I love a good model. They make sense. We get along. Models are used in a number of different contexts: Hydrological, Climate simulation and Agriculture. Crop models are a recent development, mirroring the trend in increased popularity of modelling in academic geography.

So what is a crop model? (Stay with me, I know this could be a bit intense if you are not a model lover like myself). The aim of a crop simulation model is to estimate crop yields as a function of certain parameters including weather, soil conditions and potential agricultural management policies. This is done by firstly simulating natural conditions. Certain parameters (within the model) are altered in order to create probabilistic future scenarios (such as changes in soil moisture), thus allowing future crop yields (under these scenarios) to be calculated. A classic example of this would be predicting the effects of changes in precipitation, as result of climate change, on agricultural yields (Kang et al., 2009). 

The use of these models is particularly relevant to agricultural in the African regions. Exponential population growth and climate change are both factors which will put pressures on the African agriculture sector. Based on this premises crop models (in combination with development models) should be incorporated into future policy decisions (Dourado-Neto et al., 1998). 

Crop Modelling is becoming more common in academic research (Argawall and Mall, 2002; Tubiello et al., 2000). However, as with all modelling studies, a certain level of uncertainty is associated. This uncertainty is something I wish to address in a later post so will not bore you with the details now.

This was just a brief introduction to the overall aims of crop modelling. Over the coming few weeks I hope to explore the different applications (and coinciding crop models) of agriculture studies, the uncertainty associated with crop modelling and how these models can help achieve sustainable agriculture. 

Keep it Growing

Climate change and exponential population growth have both been identified as pending threats to future agricultural production (Sivakumar et al., 2005). Such pressures have stressed the need for achieving sustainable agriculture. The idea of achieving sustainability in the agricultural sector has been discussed extensively in both academia and politics (Garnett et al., 2013; Netting, 1993). Yet this is still yet to be achieved!

Chapter 14 of Agenda 21 states by the year 2025, 83 percent of the expected global populations will be living in a developing country.  Agriculture has yet to meet the demand of the present day without incorporating future needs. There is an urgency to meet these demands by increasing production of already cultivated land, whilst avoiding further encroachment on land unsuitable for agricultural use.

Figure 1: Timeline of the term Sustainable agriculture. Demonstrating the extent to which it has been discussed on a global scale. 

This topic has been discussed extensively (demonstrated by figure 1). Most recently the ideology of achieving sustainable agriculture has been incorporated within the sustainable development goals (United Nations, 2015). Sustainable Development Goal Two: focuses on ending hunger. It aims to address the issues surrounding hunger, food security and malnutrition through achieving sustainable agricultural. Target 2.3 established issue of increased demand for food production with an aim to double agricultural yields by 2030.

Thoughts and reflections:

The sustainable development goals will have positive implications. Bringing the attention and consequently funding to the issues of agriculture will never be negative. Despite not meeting the targets, the MDGs focused donor funding and encouraged some progress on the topic of hunger (the level of hunger dropping by 27% since 2000) (Sachs, 2012). Hunger is still currently an issue in Sub Saharan Africa as 23.8% of the total population are classed as chronically undernourished (Global Hunger Index, 2015). Furthermore future predictions of population growth (8.5 million by 2030) need to be encompassed into the target of the SDG goal 2.3. The predicted “doubling” in agricultural production will need to incorporate not only the current gap in hunger but also the expected population growth, currently it is unclear if this has been accounted for. However uncertainty, associated with the extent and rate of population growth, may prevent this target from being ever effective in achieving sustainable agriculture and preventing hunger. 

Happily ever after: The tale of water and food.

 “To reduce poverty and assure food security, African agriculture must grow at 4 to 5% per year, more than twice the rate of recent decades” (Dowswell et al., 1997).  

As mentioned above agricultural expansion (be patient! This will be covered in next weeks blog) is essential in ensuring food security. Despite being dated, the theology of the quote is still relevant. Especially when considering the implications on future population growth and climate change on agricultural demand (Fereres et al., 2011). This post will explore the theology surrounding the food-water relationship and discuss the ways in which Africa could gain food security.

Food Security is defined by the World Food Summit (1996) as “existing when all people at all times have access to sufficient, safe, nutritious food to maintain a healthy active life” (WHO, 2012).

The relationship between food security and water resources is not a complex one. Water is a restricting parameter of agriculture. This becomes particularly noticeable within Africa, due to the concentration of water scarce regions (stressed within my first post). Lack of reliable water sources (as a result of erratic and seasonal rainfall patterns) can result in famine and under nourishment, especially in areas which are reliant on agricultural based incomes.

Given the competition for water resources in the agriculture sector and uncertainty associated with future climate change, the examination of this relationship is vital. Lobell et al. (2008) used a series of crop models to predict changes in agricultural production to 2030. The paper indicated reduced crop yields will be a resulting factor of climate change. In many cases this will create a state of food insecurity. An alternative option, to mitigate this, would to be increase imports of food from regions which will not be effected as badly by future climatic changes (virtual water). Sourcing food from a variety of sources overcomes the localised risks of food shortages (i.e. if drought is an issue in a local region, it is not likely to influence crop growth in other countries), thus increasing food security (Allen, 2012).

However this in itself is not a solution. As outsourcing commodities, in a bid to increase security, will undermine the wish to be self-sufficient. For many countries in Africa this will not be economically viable. In addition to modelling crop patterns, Lobell et al. (2008) predicted there will also be a increase in commodity demand and decreased supply of corn, wheat and rice. As food shortages become a global issue a rise in global food market prices is anticipated (FOA, 2007). Whether African countries be able to keep up with such a rise is controversial and reliant on their future economic development.

Africa’s water crisis. Why should you care?

Take a second and just think. There is 1,400 million cubic km of water in the world.  Of this 45 000 cubic km are available in fresh water resources (FOA, 2010). So why does 345 million of Africa’s population still live in a water scarce environment (United Nations, 2013). Is it just me who thinks this is crazy?

Water scarcity is a major global crisis, with a particular focus in African regions. Hydrologists define the term using population to water equations, accounting any value below 1700 cubic meters per capita as the minimum threshold water requirements for agricultural, energy and industrial production. The Human Development Report states irrigation for agriculture accounts for more than 80% of water consumption in Africa. Uncertainties surrounding future access to reliable water sources makes the water-agriculture relationship an intriguing topic.  

The map illustrates the concentration of water scarce populations in Africa (United Nations, 2012)

Africa’s population has doubled within the past 30 years. The most direct consequence of this exponential population growth is the heightened demand for food. Despite this need, cereal growth has only increased by a proportion of 1.8 (United Nations, 2013). Agricultural production needs to increase. Irrigation, on both a small and large scale has been explored, as a solution to this issue. Yet are there freshwater water resources available for such use? If so, then is the rate of extraction, needed to support a population growth, sustainable?

Why should you care? You like mange tout (I mean who doesn’t?!?) Then read on.

Water scarcity, experienced in Africa, will only intensify as impacts of climate change become more apparent (climate change being one of many parameters which may threaten the reliability of water sources). The implications associated with a reduction in fresh water resources may be felt on a global scale.

So, mange tout. Kenya is one of the largest exporters of leguminous vegetables (peas, beans, mange tout) globally. In 1988, exports of such vegetables stood at 3,800 tonnes, by 2005 this had risen to 25,000 tonnes (RGS, 2006). Increased food demand and limited water supply may result in a drop in agricultural productions, so say good bye to your beloved mange tout…

Over the next few months, through this blog, I will be exploring the debates surrounding water and agriculture in Africa. I will begin by addressing topics such as the limitations to irrigating, physical and socioeconomic restrictions to water access, gender inequality in agriculture and much more. A particular area of interest which I will aim to address is the future risks and predictions to the water-agriculture relationship such as the influence of climate change, unsustainable levels of ground water extraction and any the political implications surrounding these.

So remember, this is not just Africa’s crisis. You should care.