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Agriculture impacts groundwater, but how do we sustainably feed our growing populations?

Writer's picture: Dennis M. NjungeDennis M. Njunge

Introduction


Food and water are among life's most important themes and enablers for humans, animals, and plants. Without food and water, existence on Earth would not be possible. For human beings, food production is predominantly through modified agriculture which involves the alteration of the condition involved in growing plants. In providing food to the rapidly growing global population, agriculture uses approximately 70% of the global freshwater water supply (Barbier, 2019). Notably, while fresh surface water is only 1.2% of the global water freshwater, most irrigation water is drawn from groundwater sources representing 30% of global freshwater resources. (Barbier, 2019).


Over the last three decades, many agricultural inputs have been used to enhance production without deliberately being cognizant of certain compounds' effects on the environment and water resources (Moss, 2008). While Carson (1962), in her book, 'Silent Springs,' expounded on the impacts of pesticide use, the beneficiaries criticized it. However, there is evidence of the disruption of agriculture on freshwater systems from their pristine state (Moss, 2008). Given the importance of agriculture and water independently and the dependence of agriculture on water for irrigation, it is important to understand each system and how each impacts the other.


Groundwater quality and agriculture


Agriculture is the modification of landscapes to produce goods used for sustenance or market, whether eaten or used in other ways by settled human societies (Moss et al., 2014). Over time, there has been a huge diversity in the intensity at which agriculture is carried out across different geographies in the world. In the global south, for example, with communities and economies dependent on agriculture, there is a combination of subsistence and plantation farming. In contrast, in the global north, agriculture is predominantly large-scale. An estimated 10 billion hectares of natural systems will be converted into agricultural land by 2050 (Tillman et al., 2001).


On the other hand, groundwater is the water stored below the Earth's surface, usually in soil pores or rocks while water quality is water's chemical, physical and biological characteristics with respect to its suitability for a particular purpose (Hiscock, 2005). Given the complexity of the ecosystems, anthropogenic activities have taken little consideration of the effects of land-use changes on habitats, hydrological cycles, and chemical cycles. Inputs used in agriculture, such as pesticides and fertilizers, are made of compounds containing phosphates and nitrates, often added to the soil without proper evidence of the amounts needed. As such, most are not used up, dissolving into water during rainy seasons and forming solutions that are carried into water bodies through runoff and ultimately infiltrating into groundwater sources. While the residence time it takes to infiltrate depends on factors such as the lithology of the geological materials, the area's geological structure, and the landforms' geomorphology, the possibility of contamination remains eminent (Hiscock,2005).


Moss (2008) looks at agriculture as 'Kali,' the Hindu goddess of destruction. He notes that agriculture has not had a net positive effect on ecological functioning, particularly freshwater resources. Looking at the negative and positive aspects of agriculture on groundwater quality, our analysis fails to note any positive aspects but recognizes the need to feed the growing populations. Intensive use of nitrogen fertilizers in the last three decades has significantly increased chemical use, resulting in serious groundwater pollution (Hellberge, 1987). In preparation of land for agriculture, activities involve clearing natural vegetation without regard for the biophysical impacts. In some instances, it has involved the draining of the wetland ecosystems that are minerotrophic hence creating a pathway for the pollution of groundwater resources. Little regard has been given to the functional nature of these freshwater wetlands in providing the needed conditions for the movement of organisms between terrestrial and aquatic boundaries, whose function in breaking down pollutants can not be overemphasized.


Moreover, with intensive farming, pesticides and fertilizers continue to be slowly infiltrated into groundwater. Depending on the chemical composition, rock interaction may create compounds that find their way into the groundwater aquifer. This has been documented in Slovenia, where there have been serious cases of pollution by nitrates leading to the development of a nitrates directive. In areas with chalk, it is possible that pesticides can be transported through the fissure system (Hiscock, 2005). Worse, pesticides affect water chemistry with the possibility of eutrophication and food web modification (Moss et al., 2004).

Finally, livestock farming produces many waste products and pathogens. One common pathogen is Cryptosporidium which is presently a challenge in the UK. Excreta from the animals, which in most cases is not well managed, find ways into waterways introducing pathogens to surface water and groundwater sources. Pesticides and herbicides are one of the biggest inputs in animal and plant husbandry. While different pesticides have different concentrations and toxicity, they can easily penetrate groundwater sources in areas where the water table is low.


Conclusion


In conclusion, agriculture disrupts all freshwater systems from their natural state (Moss, 2008). Both plants and animal farming negatively impact the water in quantity and quality. Through agricultural activities, pesticides, herbicides, and fertilizers that contain phosphates and nitrates are introduced into the environment. Poor management and overuse of these farm inputs lead to transportation through various modes. Ultimately, they are deposited in water systems. Groundwater contamination is not immediate; pathogens and compound leach and flows through rock structure, reaching the water table. These compounds and pathogens are sometimes deposited inadvertently through farms' wells, contaminating groundwater.


However, as much as the world needs to be fed, sustainable agricultural practices must be deeply thought through and invested in. Water is finite, and unsustainable exploitation can only lead to insecurities in the future. Therefore, understanding the water use, land use, and agriculture production nexus should not be a theoretical approach but a practical, actionable, and bankable model.




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