Agriculture uses 70%
of the Earth’s surface freshwater, which makes it comfortably the greatest
consumer of freshwater. Because of this great thirst, it has a central control on the health and
sustainability of freshwater ecosystems, and the biodiversity such systems
support.
The world’s
freshwaters support up to a third of all vertebrates and at least 40% of global
fish diversity, and when considering that they only make up 2.5% of the world’s
surface water, freshwater ecosystems are a vital source of global biodiversity.
What concerns many scientists is the increasing threats facing freshwater
biodiversity, of which agriculture is a significant one.
Continuing intensification, with greater applications of artificial fertilisers and pesticides, and expansion in response to growing global populations, as well as inefficiency in freshwater usage (60-80% is lost via evaporation and seepage), mean that agriculture is threatening freshwater biodiversity. As the graph below demonstrates, sourced from Martin Jenkins’ journal article for Science, over the last 30 years freshwaters have suffered most in terms of biodiversity degradation. This coincides with an intensification of agriculture worldwide.
Continuing intensification, with greater applications of artificial fertilisers and pesticides, and expansion in response to growing global populations, as well as inefficiency in freshwater usage (60-80% is lost via evaporation and seepage), mean that agriculture is threatening freshwater biodiversity. As the graph below demonstrates, sourced from Martin Jenkins’ journal article for Science, over the last 30 years freshwaters have suffered most in terms of biodiversity degradation. This coincides with an intensification of agriculture worldwide.
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| Species population indices for forest, marine, and freshwater ecosystems, as included in the 2002 WWF Living Planet Index (Source: Jenkins, M. (2003) in Science, 302) |
David Dudgeon andcolleagues go as far to say that ‘freshwaters may
well be the most endangered ecosystems in the world’ (2006: 164), and I would
be inclined to agree in face of the evidence. The Aral Sea and Lake Victoria
provide two definitive examples of how human interference, and in particular
the contributions of agriculture within the catchment, have decimated
freshwater biodiversity. Inefficient and unsustainable freshwater use and
immensely excessive chemical applications led to the demise of the Aral Sea and
the biodiversity it supported. Similarly, the contribution of agricultural
intensification in the catchment of Lake Victoria exacerbated aquatic
biodiversity degradation.
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| Satellite imagery showing the shrinking of the Aral Sea, Central Asia (Source: www.fansshare.com/aralseadesertification) |
Agriculture –in
particular intensification and unsustainable water usage – has severely damaged
freshwater ecosystems in the recent past, and with the trend of intensification
and expansion expected to continue, the threats to freshwater biodiversity currently
posed by agriculture will only increase. There is a real need for agriculture
to become more sustainable and efficient globally, and to specifically
recognise how intensification or expansion in a particular region will impact
freshwater ecosystems. The ignorance of the Soviet Union, in regard to
implications on the Aral Sea of cotton production in Uzbekistan, is a real
example of how damaging a lack of awareness can be for freshwater biodiversity.
If the world’s current freshwater biodiversity decline is to be curtailed, such
mistakes cannot be repeated.
If we can quench agriculture's great thirst for freshwater globally, or certainly reduce how much it spills from its glass, then that will be a real step in the right direction for freshwater biodiversity.
Hi Hugo,
ReplyDeleteI completely agree with this post, you've summed the issues up well. How do you suggest agriculture can become more sustainable and efficient when it comes to water use? Also, I know you live on a farm and I wonder to what extent water use is considered on UK farms?
Hi Rachel,
DeleteFor me, the first port of call would be to improve the efficiency of water application, as current common methods of irrigation often generate large amounts of leakage. Also, these methods – such as centre pivot irrigation – irrigate areas that already have sufficient moisture or even irrigate uncropped areas, essentially spraying water blindly. There are other methods of irrigation, driven by technological improvements, which are more precise. One example is Variable Rate Irrigation, which allows farmers to selectively turn off specific nozzles on centre pivot irrigation systems as the pivot moves over patches that don’t require water. This means that unnecessary irrigation is tackled, thus reducing water use and so improving sustainability.
Another example of how technology is capable of combatting unsustainable water usage involves the direct measurement of soil water content (through microwave remote sensing) to be used as an informative tool, so that irrigation can be scheduled for times when the crops need it and only in the areas needed.
Alternatively, entirely different irrigation techniques could be employed, which consume much less water. Subsurface drip irrigation systems minimise the amount of water lost due to evaporation and runoff. Here is a great article that goes into more detail about drip irrigation if you want to know more: http://www.unilever.com/sustainable-living/water/agriculture/.
Of course, many of these options rely on new technology, and are therefore expensive. But already proposed in the USA are subsidies in place, and so they are becoming more viable options for improving the sustainability and efficiency of agricultural water use.
Rainfall harvesting, fixing leakage points, and the use of treated wastewater could provide more cost-effective solutions. Conservation tillage, whereby cover crops are used and plant residues are left in the field, is another way in which water use can be reduced, as such techniques improve the soil’s capacity to hold water and even lower soil temperature so that less water is lost through evaporation. Even a change in our diet could help, as meat and dairy products require greater amounts of water.
There is some potential for genetically modified crops to play a role too, with the development of drought-resistance. However, I would take the stance that a change or improvement in irrigation practice would generate a greater reduction in water use.
I hope that provides some examples of how agriculture can become more sustainable in terms of water use and answers the first of your questions.
From a personal perspective, I feel a lot of debate on reducing agricultural water consumption focuses on developing countries, and perhaps this isn’t so surprising considering this is where populations are growing and hence agricultural areas expanding and demand for irrigation increasing. I would say that debates in the UK are lagging sometime.
As you mentioned, I do indeed live on a farm, and I have spoken to my father about issues of water usage. What became evident from these conversations is that these problems aren’t so pressing in the UK as in other countries such as the USA and in the Mediterranean, perhaps predominantly down to climate and threats of loss through evaporation. Currently, UK farmers are encouraged to stop leaks in irrigation piping to improve efficiency, and to irrigate at times of day where evaporation will be minimised (a figure of 30% less loss through evaporation at night compared to day was thrown at me by my old man!). There are also restrictions on water use for irrigation in southeastern UK, where there is a lot of thirsty agricultural production coupled with drier conditions.
I would have to say that there are some considerations in the UK over water use, but currently these issues are more severe in developing countries or those warmer in terms of climate and as a result this is where global debate focuses.
Apologies for the mini-essay, but I hope I’ve answered your queries fully!