Soy's Water Footprint II: A Complex Picture

In the previous article I introduced some of the issue related to water consumption as a result of soybean mass production at a local scale as well as the regional impacts that such water footprint would have on the environment. However, the more I read about this issue, the more I began to grasp the complexity of such implications. 

I concluded that soybean agriculture was indeed "bad" for the environment in terms of local freshwater withdrawal, but many more questions arose as a result: 

how does soybean compare to other major crops on a global, rather than local, scale? Should we abandon this crop or is this the "least bad" of our options? 

Let's first take a step back and consider why water footprint is an issue that I should be considering when evaluating the environmental impacts of agricultural crops. 

The water footprint calamity

Global freshwater use has increased by 600% in the 20th century, leading to the belief that by 2025, at least 2billion people will have experience the direct effect of water scarcity. Moreover, a UNESCO report in 2006 exposed the dangers of freshwater exploitation: 

studies found that up to 80% of the world population will suffer from water scarcity in the near future and the situation will only get worse as current trends in food and energy demand inevitably increase.

The current global water footprint (as an average of values between 1996 and 2005) is 9087 GM3/year, with cereal, meat and dairy products being the major contributors. 

So does agriculture play this big of a role? 

The answer is YES Studies estimated that between 85% and 92% of all water consumed at  global scale is for agricultural purposes, with irrigation alone accounting for 70% of total yearly freshwater usage.  

It is important to highlight that water scarcity and stress do not automatically or necessarily match high levels of water demand. In fact, water footprint considers both the amount of water readily available and the amount that is being demanded. Moreover, not all water consumption is the same, and in order to manage and control water footprint, it is necessary to distinguish between different types of usage. 

Firstly, blue water is the water that can be directly extracted from rivers and reservoirs, whereas green water is the one enclosed in the vegetation or within the unsaturated soil layer. 

Recently, the concept of gray water was added to the former two to highlight the critical importance of pollution in freshwater consumption. Gray water is essentially the amount of water that is required to assimilate pollution from a certain source - usually it is composed of washed off water from crop fields containing fertilizers and pesticides. 

Freshwater demand is inevitably going to increase over the future decades due to increasing global population and economic development. However, as freshwater demand increases, there is a risk for supply to decrease as a result of climate change leading to even less security. Climate models predict that precipitation patterns will change and droughts will become a much more prominent issue as the global temperatures rise, leading to even more complexity in the distribution of this fragile resource. 

The global picture

As mentioned above, cereal take up a vast majority of the water footprint on the global scale. In fact, wheat alone requires 1087 Gm3/year. Other crops the require high inputs of water are rice and maize, with values of respectively 992 Gm3/year and 770 Gm3/year. The figure below illustrates rather effectively the distribution of total water footprint amongst crops. 

Global contribution to water footprint by different crops

This image immediately sparks up an interesting point: soybean may be causing dramatic impacts at a local scale but on a global one there are crops we should be more concerned with. The water footprint associated with soybeans only make up 5% of the global picture, so really it's not that bad...

But HOLD ON A SECOND: these percentages account for the total footprint of the crops, and cannot be directly compared because some of them are more popular than others. If I produce 100kg of wheat and 1kg of soybeans then it is most likely that the wheat production will have a higher water footprint. 

We should further investigate how soybean agriculture impacts water footprint PER TON of crop produced, as well as analysing whether the water footprint is green, blue or grey. The table below provides much more detailed information: 

Broken down water footprint for major crops 

  

With a global footprint of 2145 m3 per ton of crop, soybeans have a much higher environmental impact than rice, maize and wheat!

In simple terms, if soybean agriculture were to expand to the same amount of wheat produced on a global scale (estimated to be around 16.68m tons in 2015), its water footprint would be almost 20% more of what is currently caused by wheat. 

On the other hand, it is also important to remember that most crops have much higher gray footprint impact than soybeans so this could be a safer option in terms of pollution. 

Is soy's water footprint Sweet or Sour?

There is no simple answer to the complex issue of water footprint: an hierarchy of scale across a highly heterogenous range of crops creates a complex scene that makes it difficult to come to a conclusion as to wether soybean is destructing or could potentially save our planet. In terms of global footprint, an increase in soybean agriculture would lead to exceptional increase in water withdrawals, but at the same time could potentially benefit the environment through reducing water pollution levels. 

Let me know what you think in the comment section below!