Land use change is majorly driven by the expansion of cropland and intensification of agricultural activities, with the soybean being the most important agricultural output in the Brazilian landscape. Demand for food products and energy sources is ever rising and soybean plantations have rapidly taken over the natural environment in parts of the Amazon forest.
This process clearly has a number of environmental consequences
that will later on be discussed and considered in this blog, but I will start
from taking into consideration the impact that land use intensification
connected to soybean cropland has in terms of water footprint.
I will explore the changes in water
quality, quantity and catchment hydrology that are connected to the new land
use patterns due to soybean expansion. Moreover, I will place my discussion the framework of the freshwater planetary boundaries and the relative consequences of soybean mass production on the regional
as well as global ecosystems.
Water Quality
Firstly, the soybean, just like other
legumes, requires great quantities of nutrients in order to flourish,
regardless of the local climate conditions. The introduction of chemical
fertilizers is bound to cause local contamination of water sources and lead to
changes in the regional aquatic ecosystems. In fact, a
rapid flash rise in nutrients can be devastating for habitats as it causes eutrophication
and it accelerates the growth of algae and consequently a decline in light
available to the living organisms.
Moreover, the washed off chemicals can lead to
declining levels in groundwater quality. Chemicals contained in the fertilizers, such
as lead and cadmium, can have negative consequences for the local flora and
fauna.
Water Quantity
Secondly, the tropical forests and local
climate patterns pivots around evapotranspiration.
If vast amounts of canopy are destroyed, then naturally less precipitation will
take place.
Studies have found that rainfall in the tropical forests in Brazil will decline by 20% by 2050 purely as a result of recent and predicted deforestation rates.
As less moisture is
reintroduced into the water cycle and deforestation drives a decline in
precipitation, the ecosystems will begin a slow and dangerous drying process. Land
use change will also lead to higher surface temperatures and in
turn this could cause higher evaporation rates and -unfortunately- even worse
water balance levels.
The Tapajos river basin
Let’s take a step back and look at an
example of the direct consequences that soybean agriculture can cause on a
region’s water cycle. A very recent review of the water footprint of soybean
agriculture in the Amazon has opened my eyes to the extent of the danger of
such rapid land use intensification. The study considers both water use and
pollution around and within the cropland area as well as in the entire water
catchment.
As expected, the water footprint will rise considerably by 2050, but by how much?
As expected, the water footprint will rise considerably by 2050, but by how much?
The study finds that 1.8% of the study area
will face threat posing or unsustainable water scarcity levels, with a 15%
increase in the locations that are just about within the limit of
sustainability.
Moreover, for what regards water quality, over 10% of sites in the study area will present unsustainable or threat posing levels of pollution within the next 40 years. These values did not strike as particularly worrying until I consulted the planetary boundaries recently discussed by Will Steffen.
Moreover, for what regards water quality, over 10% of sites in the study area will present unsustainable or threat posing levels of pollution within the next 40 years. These values did not strike as particularly worrying until I consulted the planetary boundaries recently discussed by Will Steffen.
Planetary Boundaries
The current freshwater boundary level for sustainable use at basin scale is expressed as the ratio between water withdrawal
and the mean river flow – and is set at 55%.
Similarly, in the Tapajos river
basin study, water scarcity is calculated as the ratio of water footprint (or
more simply the amount of water withdrawn to be used in the soybean production)
and water availability in the catchment.
A simple cross reference of these two papers confirms that only in the Tapajos river basin, an area equivalent of 147,730 football fields (!) will have surpassed the local freshwater planetary boundary by 2050.
Before you panic…
When talking about planetary boundaries I believe it is necessary to begin a self-critical discussion on the hierarchy of scales.
If like in this case one boundary is overcome at a local scale, I shouldn't necessarily assume there will be "sour" global implications. And at the same time a global variation in freshwater use or even climate change may not have local repercussions.
If like in this case one boundary is overcome at a local scale, I shouldn't necessarily assume there will be "sour" global implications. And at the same time a global variation in freshwater use or even climate change may not have local repercussions.
Different
planetary boundaries are applied at the same time over a variety of spatial and
temporal scale and leading to a very complex picture of how we make sense of
resilience. There are clear limitations to this framework but it is widely accepted
that at a local scale it is a solid starting point for the development of
management strategies to support sustainability goals.
We have established that soybean agriculture is a remarkable water footprint calamity, but is it worse or possibly not as bad as other crops?
In the next article I will explore the global changes in freshwater use and water footprint associated with agriculture and further investigate the hierarchy of local-global scales.
In the meantime feel free to leave a
comment below or tweet me!
Doese Soybean agricultural brings positive effects for food? And compared to other simolar agricultural the soybean has more positive or negative effects?
ReplyDeleteDoese Soybean agricultural brings positive effects for food? And compared to other simolar agricultural the soybean has more positive or negative effects?
ReplyDeleteHi Nature, thank you for you question!
ReplyDeleteSoybean agriculture quickly expanded thanks to its exceptional content in protein, and as a result became one the most widely used feeder for animals. As this is clearly not an animal protein it is considered to be safer - especially in terms of the mad cow disease. In that sense you could say it has a positive effect on overall food production as it supports the meat industry, but at the same time is that the most sustainable use we could make out of this crop given the environmental impacts of such industry?
Why not skip that step and encourage consumption of soybeans directly? This will all be discussed later on!
Moving on to your next question, the soybean is quite exceptional and the centre of attention because of it's incredibly fast expansion on the global market in the second half of the 20th century. My next article will try and compare the ecological footprint of the soybean with the one of other commodities such as corn, wheat and rice but it is necessary to keep in mind the idea of temporal as well as spatial scales in changes and impacts!
Mia