PhD Proposal: Influences of women on the agricultural sector and rural communities from the interwar period through 1950 in England.

Title:

Influences of women on the agricultural sector and rural communities from the interwar period through 1950 in England.

Background:

Gender identity roles within rural farm laborers changed drastically during the first and second World Wars in Great Britain. With men called upon for the war effort during the First World War, women were recruited to assist in the new Land Army and leave their homes to work within the male-dominated agricultural sphere (Goodman and Mathieson, 2014).  Their competency and tenacity assisted in changing the view of a woman’s place and capacity throughout the nation, including spurring on the newly created suffragette movement which gave a voice to nearly half the population leading to Votes for Women! finally being secured (Riddell, 2018). While many women returned home following the war, others continued their volunteer work in the new Women’s Institute (WI) (1915), the British Red Cross, and the YMCA National Women’s Auxiliaries (The Women’s Institute, n.d.). As the threat of a second war loomed, enrollment increased in these and other organizations, including the Air Raid Precautions (ARP) (1938) and the associated Women’s Voluntary Services (WVS) (Storey and Housego, 2018) . The WVS and WI were instrumental in assisting with the Dig for Victory campaign, the Women’s Land Army, and the national fruit preservation scheme; all three of which were tied to the creation and preservation of food for the nation (Kramer, 2008; Powell and Westacott, 1997; Storey and Housego, 2018).  

At the start of the Second World War, nearly seventeen thousand women volunteered to ‘work the land’ as part of the WLA, with eighty thousand active members at its peak in 1943(Storey and Housego, 2018). Inclusion of additional women onto farms and into the rural communities had a variety of results including the creation of agricultural colleges, regional specialist trainings, the establishment of equal pay regulations for female farm laborers, and established weekends, holidays, and sick leave (Ambrose and Jensen, 2017). Women took on a variety of roles within agriculture, from working in the Timber Corp to running poultry farms, to working in agricultural gangs (Geere, 1987). However, they did so from both urban and rural environments. Smaller homesteaders were not always registered as agricultural holdings, yet this did not dissuade women from managing smaller holdings to assist with urban and suburban farming (Ball, 1989). It also brought women out of the cities and into the countryside and affected the rates of marriage, child birth, and divorce (Perry, 1968). These changes in population, with a baby boom following the war years both in 1921 (~357,000 males and 385, 000 females aged 3-4) and in 1951 (~430,000 males aged 3-4; ~409,000 females aged 3-4) (Neilan, 2014), coincided with increased marriage rates at the start and end of the war, followed by an increase in divorce and adoption rates at the end of the war (Office of National Statistics, 2015). Some of these can be attributed to new legislation, but others show a trend in the separation of family finances and the ability for women to manage on their own away from a husband’s watchful eye (Perry, 1968).

Objectives and Research Questions:

While women have always held a role in agriculture they were often placed into the role of ‘farmer’s wife’ or ‘farmer’s daughter,’ not simply ‘farmer’ (Ball, 1989; Sachs, 1983). Changing attitudes of today can be traced back to the various Land Armies and Friendly Societies of the World Wars and while women own and operate both small and large scale farms, are active in every level of the supply chain, and develop agricultural policies, current views of femininity and women’s roles in society seems to be making a paradigm shift across the world (Ambrose and Jensen, 2017). However, current literature focuses on the relationship between fertility rates and women’s employment (Engelhardt et al., 2004; Joshi and Hinde, 1991), the changes in agricultural education (Brook, 2011), women’s underrepresentation within census data (Higgs and Wilkinson, 2016), feminism and legislative reform (Lewis, 1985), and the state of agriculture and spheres of women’s influence (Anderson, 2014; Fairbanks and Haakenson, 2017; Whatmore, 1991). While focused on the microspheres these questions entail, few broad-spectrum approaches take into account how women’s influences on farms and in the rural community change the very foundation of basic family lifestyles, such as food choices, migratory patterns, changes in voluntary service work, agricultural supply chains, and changes in family dynamics. Considering these aspects, this research is a timely analysis of the role women play, both in the public and private spheres of agriculture and rural communities.

It is this broader view that we will focus on including the following questions:

• Did the addition of women onto farms (during /after WW1&2) beget a reversal of two centuries worth of migration leading to the growth of rural villages and towns?
• Did the relationship between working women change the dynamic for the modern family unit?
• Did women’s farming activities create a ‘new norm’ when discussing women’s capabilities?
• Did the inclusion of women onto farms change the management or practices of farms beyond the technological changes of the time period?
• Did the technical training of women for farm work create, assist, or alter women’s entry into the supply chain?
• Did women’s roles during/after WW1&2 alter the food choices of the nation?

Methodology and Planning:

This research hopes to answer the knowledge gap of how women have influenced the agricultural sphere within the context of rural community. It dovetails with the concepts of rural identity and femininity and is intended to employ archaeological and landscape techniques and utilize the insights derived from quantitative history, and modern literary and gender studies within the lens of the agricultural landscape.

Initial investigation will include a thorough literature review of the data available to date. Following such an investigation, interviews will be used in conjunction with material from autobiographies, contemporary social surveys, farm record books, commentaries by social investigators, census data, and diaries (Strange, 1999) as both primary and secondary source materials. Additional research will be carried out at the History of Food and Drink in the Institute of Historical Research Library at the University of London and the Museum of English Rural Life (MERL) in Reading.

Planning will follow the University of Readings’ (UoR) anticipated format of initial inquiry during year one, research and review in year two, and final paper creation in year three. The final output will include a course curriculum design along with the paper. The design will be structured upon the Universities’ eleven week semester and will follow a four-four-three pattern focusing on Women and Rural English Identity in section one, Women and Rural Development in section two, and a localized assessment project in section three. The goal of creating a curriculum is two-fold, firstly, it acts as an outline to the paper and secondly it becomes a usable product for the University at the end of the research.

Sample Course Design (initial thoughts):

·         Section 1: Women and Rural English Identity

a.       What does Rural Identity mean?

b.      Historical context of rural women’s roles:

                                                              i.      Peasant

1.      Farm Laborer

2.      Servant

                                                            ii.      Crofter

1.      Supplier

2.      Tenant

                                                          iii.      Middle class

1.      Landlord

                                                          iv.      Upper Class

1.      Aristocracy

c.       The interwar period:

                                                              i.      Identification of women’s roles in rural communities.

1.      Agriculture

2.      Service and good will

3.      Home and family

4.      Incorporated Land Girls

a.       Public relationships and perspectives

d.      World War Two:

                                                              i.      Identification of women’s roles in rural communities.

1.      Agriculture

2.      Service and good will

3.      Home and family

4.      Incorporated Land Girls

a.       Public relationships and perspectives

e.       Post-War period:

                                                              i.      Identification of women’s roles in rural communities.

1.      Agriculture

2.      Service and good will

3.      Home and family

4.      Incorporated Land Girls

a.       Public relationships and perspectives

·         Section 2: Women and Rural Development

a.       Influences on modern agriculture

                                                              i.      Gender Identity: what it means to be a Female Farmer

                                                            ii.      Agricultural Research

                                                          iii.      Supply-chain management

1.      Food selection, nutrition, and cookery

2.      Suppliers, owner/operators, and transportation

                                                          iv.      Policy development

b.      Family structure

                                                              i.      Marriage, Divorce, and Family Units

                                                            ii.      Migratory Patterns

·         Section 3: Localized Assessment Project

a.       Selection of region:

                                                              i.      Explanation of region’s rural identity

                                                            ii.      Historical context of women’s roles in region

                                                          iii.      Women’s roles in agriculture in region

                                                          iv.      Changing values or perceptions

Results/Discussion:

Census and population data from the Office of National Statistics and farm record books from the MERL will be the core of the migration research, while interviews and diary entries will show how women viewed themselves and how men viewed the women working in the sector. From here I anticipate seeing overlap within the two genders’ opinions followed by acceptance in parts of the industry (those aspects relating to home making such as cooking) and fervent dismissal/denial of other aspects (ownership, trade agreements, and policy development are my initial thoughts). Additional research will take the view of changes in agricultural practices, women’s entry and ownership aspects within the supply chain, and alterations to the family unit and rural identity.

Conclusions:

The primary goal of this research is to establish what, if any, role women had in changing the course of agriculture and how they affected the rural communities they were associated with. From here, further research could look at comparisons with modern roles women play or look at trends for women’s roles in developing nations.

Initial Bibliography:

Ambrose, L.M., Jensen, J.M., 2017. Women in Agriculture. University of Iowa Press, Iowa City.

Anderson, H.M.K., 2014. The British Women ’s Land Army: Gender, Identity, and Landscapes. Western Michigan University.

Ball, J., 1989. Little Girls don’t grow up to be farmers. Peter I. Drinkwater, Warwickshire.

Brook, L.E., 2011. From farming to farm holidays : the evolution of agricultural education and the specialist colleges in the UK Lesley Elisabeth Brook Institute of Education.

Engelhardt, H., Kogel, T., Prskawetz, A., 2004. Fertility and female employment reconsidered: a macro-level time series analysis. Popul. Stud. (NY). 58, 109–120.

Fairbanks, C., Haakenson, B., 2017. Writings of Farm Women, 1840-1940. Routledge Library Editions: Rural History, London.

Geere, M., 1987. Reminiscences of a Land Girl in Witham. Albert Poulter, Essex.

Goodman, G., Mathieson, C. (Eds.), 2014. Gender and Space in Rural Britain, 1840-1920. Pickering & Chatto, London.

Higgs, E., Wilkinson, A., 2016. Women, Occupations and Work in the Victorian Censuses Revisited. Hist. Work. J. 81, 17–38. https://doi.org/10.1093/hwj/dbw001

Joshi, H., Hinde, P.R.A., 1991. Employment after child bearing in post-war Britain: Cohort study evidence on contrasts within and across generations (No. 35). London.

Kramer, A., 2008. Land Girls and Their Impact. Remember When, Norfolk.

Lewis, J., 1985. Women and Society: Continuity and Change since 1870. Refresh 1–4. https://doi.org/10.1111/j.1467-6435.1986.tb00768.x

Neilan, C., 2014. Four charts that show the impact the First and Second World Wars had on the UK’s population [WWW Document]. CITYA.M. URL http://www.cityam.com/1415708792/four-charts-show-impact-first-and-second-world-wars-had-uks-population (accessed 5.21.19).

Office of National Statistics, 2015. Victory in Europe Day: How World War II changed the UK [WWW Document]. URL https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/articles/victoryineuropedayhowworldwariichangedtheuk/2015-05-08 (accessed 5.21.19).

Perry, P.J., 1968. Working-Class Isolation and Mobility in Rural Dorset, 1837-1936: a Study of Marriage Distances.

Powell, B., Westacott, N., 1997. The Women’s Land Army. Sutton Publishing Limited, Gloucestershire.

Riddell, F., 2018. Suffragettes, violence and militancy [WWW Document]. Votes for Women. URL https://www.bl.uk/votes-for-women/articles/suffragettes-violence-and-militancy (accessed 5.28.19).

Sachs, C.E., 1983. The Invisible Farmers: Women in Agricultural Production, 1st ed. Rowman & Littlefield Pub Inc, Totowa.

Storey, N.R., Housego, M., 2018. Women in the Second World War. Shire Publications, Oxford.

Strange, D., 1999. A Land Girl’s Diary: Burnham 1948.

The Women’s Institute, n.d. The Women’s Institute [WWW Document]. FAQs. URL https://www.thewi.org.uk/faqs (accessed 5.28.19).

Whatmore, S.J., 1991. Farming Women: Gender, Work and Family Enterprise. Springer, Hampshire.

Assessing the effect of land cover on organic carbon concentrations in European soils under various pedoclimatic conditions, using the LUCAS database

Assessing the effect of land cover on organic carbon concentrations in European soils under various pedoclimatic conditions, using the LUCAS database

DINGKUHN, Elsa; LATHEROW, Tamisan; LAUBRIET, Valentin; LOMBARD, Lucie

  

Abstract

The soil represents a large carbon sink that plays a major role in the carbon cycle and ultimately on the climate. There is a growing interest to understand the mechanisms that affect SOC at a large scale in order to adapt environmental policies. The Joint Research Center alongside with EUROSTAT has created data (LUCAS) points which enable researchers and the general public to monitor Soil Organic Carbon (SOC) concentrations in soils across Europe.

Based on an extensive literature review, we confirmed the assumptions that climate, soil texture and land cover are key determinants of SOC concentrations through use of the LUCAS data points. We focused on the impact of land cover on SOC concentration at a European scale which was accomplished by creating pedoclimatic zones based on biogeographic regions and soil texture classes, in which we analyzed patterns between land cover and SOC. We demonstrate that different land covers under similar pedoclimatic conditions and soil textures have different SOC concentrations and that at European scale, grasslands and vineyards have significantly higher and lower SOC respectively, when compared to other crops. Cereals, maize, leguminous plants, vegetables, orchards, root crops, fiber and oil and ‘others’ did not show significant difference in SOC at a European scale.

However, these factors aren’t sufficient to explain all the variances observed, thus other potential influences need to be taken into account such as farm practices or other soil properties like aggregate size. Furthermore, substantial variability in SOC levels still occur among samples with the same land cover under the same pedoclimatic conditions, implying that this approach, although relevant, should be based on less extensive pedoclimatic zones to gain greater accuracy. In addition, the method developed in this study couldn’t be applied to the targeted scope and scale (EU23) due to limited sample sizes in some land cover and pedoclimatic cases.

Moreover, the relative influence of factors such as rainfall or temperature may vary across scales and from one biogeographic region to another, and thus may need to be attributed different relative weights. The feasibility of applying such nuances pinpoints the limits of such large scale studies. Nonetheless, this doesn’t question the meaningful benefit of LUCAS database, as it can be extensively used in research and extension to inform and guide agri-environmental policy design and land use planning.

Read the entire paper here.

Utilization of Wetlands for Agricultural Drainage Treatment: A Literature Review

Utilization of Wetlands for Agricultural Drainage Treatment: A Literature Review
By: Tamisan Latherow
October 2018

Grade B+
Abstract:

Wetlands are gaining popularity for use in agricultural waste treatments due to their natural ability to filter and fix excess nutrients, pesticides and herbicides, raising their ecosystem service valorization. With Nitrogen removal rates between 14-95% and Phosphorous removal rates between 25-95%, depending on design and infrastructure, wetlands provide a valuable tool for agricultural landscape management. However, those same services may be compromised if residence time and biodiversity of plants and microbial species are not properly managed. Mitigation efforts for restored wetlands surrounding agricultural landscapes must therefore be the primary goal of constructed wetlands for use in waste treatment and beneficial ecosystem services.

Introduction:

The world population is expected to reach 9.8 billion by 2050 (United Nations, 2017). Current estimates are that, barring all other considerations, 30% more food will need to be produced to feed everyone (Wezel, et al., 2014). To this end, many studies are focused on the creation of more food or the allocation of resources to manage supply chains, however, one must also consider the actual soil this food is to be grown on and the geospatial relationship to the surrounding landforms, catchments, and agricultural processes. How these systems interact and their influence down-stream directly impacts the efficiency of the lands’ ecosystem services, especially in wetlands. 

The Convention on Wetlands, aka. the Ramsar Convention, define wetlands as “areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres” (Ramsar Convention Secretariat, 2016). According to Ramsar, wetlands cover roughly 6% of the Earth’s surface and ecosystem services of wetlands includes water and nutrient filtration and fixation, animal nurseries and habitats, storm surge protection, erosion and soil control, and natural locations of primary food stores such as rice and fish (Secretariat of the Convention on Biological Diversity, 2015). 

Wetlands have been incorporated into agricultural land use for generations and include traditional farming practices such as rice paddies, aquaculture, terraces, and reed production for fiber (Verhoeven & Settler, 2010). Much of the world’s wetlands have either been converted to and/or border agricultural lands (Davidson, 2014) and since they are typically at a lower elevation where the natural flow of catchment systems deposit soil from upstream they are often the recipients of fertilizer run-off (Yu, et al., 2018). 

Methods:

An analysis of wetlands and their relationship to agriculture was performed utilizing over twenty articles in published scientific journals across multiple disciplines (agriculture, ecology, economics, engineering, marine and freshwater ecosystems, botany and biology). These articles covered several different spatial scales, ranging from individual wetlands to national, regional, and global wetland overviews for the past few years. They also cover both natural (limited human alterations) and constructed (man-made) wetlands, hereafter referred to as NW or CW. The articles were broken down into three categories for further review: Nitrogen, Phosphorus, and herbicide and pesticide sequestration and then discussed under the subtopic of Ecosystem Services. All were reviewed at the landscape scale of application of agroecological practice and fall under the subheading of management of landscape elements (Wezel, et al., 2014).

For the purpose of this review, agroecological processes are those agricultural processes designed to produce significant amounts of food that also follow the natural cycles of the surrounding ecosystem for such items as nutrient cycling, natural pest management, soil and water conservation, biodiversity conservation, biological N fixation, carbon sequestration, and bacteria formation and management (Wezel, et al., 2014). To quantify the data around these topics, an agroecological framework is needed. 

The framework designed by Hill and MacRae (1996) was the base for this analysis with alterations by Wezel, et al. (2014). The framework focuses on efficiency increase, substitution practices, and redesign (Wezel, et al., 2014). Within these three pillars, Wezel, et al. identify specific practices related to crops and landscapes as well as three levels of management, those being the field level, farm level, and landscape level (Wezel, et al., 2014). We shall be looking at the agricultural landscape, specifically at if the addition of wetlands [either natural (NW) or constructed (CW)] for agricultural drainage treatment benefits or hinders the wetland’s natural ecosystem services. Wetlands were chosen due to their natural filtration ability and for the fact that 64-71% of wetlands have been lost since 1900 A.D. due to anthropogenic drivers such as agriculture (Davidson, 2014). 

Results:

Various studies (Dal Ferro, et al., 2018; Darwiche-Criado, et al., 2017; Ewing, et al., 2012; Kasak, et al., 2018) have been performed to identify the amount and efficiency of wetlands to manage fertilizer run-off from agricultural lands-Nitrogen (N) and Phosphorus (P) being the two predominant chemical elements; however various herbicides and pesticides have also been studied. With the growth of industrialized agriculture and the demand for more food, fertilizer treatments have increased. However, poorly -timed applications of these fertilizers account for much of the nutrient run-off into surrounding water sources and causes algae blooms, Eutrophication, and degradation of water quality (Kasak, et al., 2018). The wetland/catchment ratio creates two types of surface flow: in-stream and off-stream (Kasak, et al., 2018). The difference between in-stream (CWs located in the flow path of the drainage water, such as a river or ditch) and off-stream (where only part of the water flows through the CW) directly impacts the efficiency of the wetland to mitigate run-off levels. Generally, the ratio of wetland to catchment should be 0.5% with a relatively low flow velocity to allow the sedimentation of nutrients and soil run-off (Kasak, et al., 2018). 

Nitrogen and Phosphorus Sequestration

The three main ways nitrogen is taken up by an ecosystem is through vegetative uptake, sedimentation, and denitrification. Natural wetlands have been shown to retain around 64% of the Total Nitrogen loading (Saunders & Kalff, 2001), but in agricultural areas, TN appears mainly as nitrate, which is not as affected by sedimentation in high flow areas. In areas with lower flow or high plant coverage, where the roots of the plants allow for higher rates of denitrification and sedimentation and contribute to a higher residence time, an increase in the rate of retention can be found (Saunders & Kalff, 2001). Most agricultural associated wetlands are off-stream systems since water inundation leads to root rot in many crops while most aquaculture activities (such as rice farming) are conducted in-stream.  The natural formation of the wetland (eg. depressions, river banks, soil type, etc.) and the density of vegetation affects the sedimentation of solids and minimizes the transport of nutrients (Uwimana, et al., 2018). 

The increase in flow rate in in-stream systems minimizes the amount of time nutrients and soil has to settle and start filtering through the wetland soil stratus (Kasak, et al., 2018). In a NW this filtration happens through several layers of soil and aggregate before reaching the groundwater and is assisted by the various natural elements in the wetland such as cattails (Typhus), willows (Salix), and other plants, as well as microbial and fungi systems. In a CW, these same processes are managed by various liners and sedimentation ponds, some of which may be planted with vegetation. Most sedimentation ponds vary in the time water flows through the system from a few hours to a few weeks whereas a NW can take years to fully filter (Kasak, et al., 2018).

Nitrogen removal is dependent on many factors, but the most important are temperature, oxygen and carbon concentrations since they contribute to the various chemical (ammonification/volatilization) and microbial functions (nitrification/denitrification) (Kasak, et al., 2018). Factors such as groundwater seepage, plant-biomass N accumulation, and oxygen stratification within the water may affect the potential for N removal. These points were thought to contribute to the increase in NO₃-N concentration over the three-year study of the Kasak, et al. paper, where as the other papers saw a decrease in NO₃-N concentrations.

When evaluating nitrate-nitrogen loading capacity, the soil’s Total Carbon and pre-loading Total Nitrogen levels were also compared between organic and mineral soils. An earlier study by Ewing et al. (2012) found that organic soils had TC (29-35%) and TN (0.7–0.9%) while mineral soils had 6–7% and 0.2–0.3%, respectively (Messer, et al., 2017). This is important since the removal efficiency of N decreased when the TC/TN ratio approaches 5:1 (Messer, et al., 2017). The ratio is an indicator if enough oxygen occurred within the denitrification process, which accounts for 93% of nitrate uptake (Tournebize, et al., 2017). If there is a lack of oxygen, the conversion of nitrate into N2O (GHG) and N2 does not occur, causing overloads in the system. Flow rates and seasonality of rainfall and fertilizer application times, (Dal Ferro, et al., 2018) as well as the OM content of the wetland (Darwiche-Criado, et al., 2017), are direct contributors to this process. These issues can be mitigated by establishing a longer residence time within the CW system, allowing for more settling and the denitrification process to occur over a longer period. Diversified vegetation is also key since plants take up different amounts of nitrates over different parts of their life-cycle and a diversified vegetation profile within the wetland allows for the maximum amount (upwards of 7%) of nitrogen removal through this process  (Tournebize, et al., 2017). This is also assisted by the variation in the plant’s carbon storing capacity. For example, Nasturtium’s have been shown to support denitrification more fully than common reed (Phragmites) in wetland systems (Tournebize, et al., 2017). 

Likewise, Phosphorus retention is also dependent on water temperature and oxygen efficiency, microbial activity and plant uptake, however the retention rates for P average only around 14% when flow rates are at their lowest allowing for a longer standing residence time (flow rate of 5 L sˉ¹) (Kasak, et al., 2018). Of that 14%, 50-70% is found within the sediment and is considered as part of the permanent reservoir (Di Luca, et al., 2017). Plant uptake and microbial activity are directly linked to the pH, temperature and oxygen efficiency as plants and microbes are most active during warmer weather with access to appropriate oxygen stores for growth and development. Research by Johannesson, et al. (2017) shows a concern over other considerations such as peak flow times for grab sampling as differences in particulate phosphorous (PP) versus total phosphorus (TP) numbers and errors based on sampling during flow-events, that is, before, during, or after major flow events have arisen which could skew the amount of TP ratios (Johannesson, et al., 2017). These questions arise because of the seasonality in loading levels and their large impact on quantity of N and P in the system due to residence time and flushing of the wetlands.

In sediments, it has been shown that pH affects P absorption, as pH increases the absorption of phosphate decreases due to competition between absorption ratio of hydroxide (OH-) and soluble reactive phosphorus (the only form of P available for plant up-take) (Di Luca, et al., 2017). This decrease in oxidation-reduction potential (ability of water to cleanse or break-down waste) and the interference of OH- reduces the absorption of P into the sediment (Di Luca, et al., 2017). Since most P in wetlands is in insoluble organic or inorganic form (dominant ratios) (Bressler & Paul, 2015), the addition of nutrients into the CW and the subsequent loss of oxygen from Eutrophication can free phosphorus from the sediment and increase the TP available for plant uptake. However, the resulting change in C:P changes the microbial biomass and rate and variability in biodiversity within wetlands, which can lead to losses of biodiversity.

Herbicide and Pesticide Sequestration

Pesticides are often a factor after application and after heavy flow events such as storms; yet, they are often less than 0.5% of the applied application with rates rarely exceeding 3% (Tournebize, et al., 2017). This is three times less than found in nitrate levels, and is typically concentrated at the head of the in-flow region (up-stream of the watershed), however there is a wide variability in the transfer and transformation process surrounding each type of pesticide (Tournebize, et al., 2017).  The transfer process for pesticides from the water to the plant (28-55%) is of concern when the transfer moves not from water to plant, but from water to animals (especially marine animals) through tissue absorption (Tournebize, et al., 2017). There is also the issue of plant material where the chemicals have moved into the interior of the plant tissue through photoaccumulation and rereleased into the system upon decomposition (Tournebize, et al., 2017). Removal of these chemicals can sometimes be carried out via deabsorbion by flushing the system with more water, but it is not always effective. 

Transfer is not the only process pesticides can go through. New molecule creation from the dissolvement or degradation of the parent chemical can also occur through transformation and while the new chemicals are often in smaller quantities, they may be no less toxic. Transformation occurs predominantly in three ways within CWs: photodegradation (the effect of sun light), hydrolysis (via the movement of water), and biodegradation (through microbial processes) (Tournebize, et al., 2017). The primary agent of transformation is through microbial processes, specifically in aerobic conditions, where some chemicals such as the herbicide atrazine, widely used in corn and sugarcane production as a weed suppressant (Hayes, et al., 2010), have been shown to have mineralization rates upwards of 70-80% (Tournebize, et al., 2017). Mitigation strategies include permitting the water level to rise and drop to allow for oxygen to be starved from the system as well as sunlight to enter and assist in breaking down the chemicals further; this creates a combination of both reductive and oxidative conditions (Tournebize, et al., 2017). Less toxic chemical alternatives such as acetochlor and butachlor have been proven to degrade quicker in wetland environments (acetochlor in the rhizosphere and butachlor via microbial process) (Yu, et al., 2018), but the solubility of these chemicals is of concern. Acetocholr’s high water solubility makes it more prevalent in the water while butachlor’s low solubility leads to higher concentrations within the soil and subsoil. Simply changing to more easily degradable chemicals does not mitigate the effects if the ratios for chemical use increase; detection rates of 75-100% for acetochlor and 88.9-100% for butachlor within the surrounding wetlands were detected in the Chinese report (Yu, et al., 2018). Mitigation efforts to remove the herbicides are available and include increased growth of C. augustifolia plants to enrich soil microorganisms which can start to break down the chemicals. Butachlor can also be eliminated from the system by the removal of soil sediments (Yu, et al., 2018). 

In areas where organochlorines (OCPs) and DDT are used in agriculture, high concentrations of the OCPs have been found in tissue samples of fish species such as Tilapia and Catfish and have been linked to higher levels in secondary predators like birds and crocodiles, and even humans (Buah-Kwofie, et al., 2018). DDT use has been linked to eggshell thinning in aquatic birds and while the concentration levels are currently not at the level of human risk, according to EU regulations, further studies should be performed to find the threshold of consumed fish contaminants in the human population (Buah-Kwofie, et al., 2018).

Discussion:

Fig. 1. Ecological framework for landscape design on agricultural lands. “Arrows represent the main research axes and point towards the research frontiers. Darker shading indicates a greater level of current knowledge” (Landis, 2017).

While the methods for collecting data were similar across the research (water tests, biomass indexes, grab samples, etc.), percentages and ratios were not consistently presented making it difficult to evaluate across zones and papers. Future research would benefit from the creation and utilization of a general health assessment guide for wetlands such as the one created by the United States Environmental Protection Agency (Office of Water, U.S. Environmental Protection Agency, 2002). Generally, it was shown that wetlands do provide a valuable agricultural agency for the removal and dissipation of harmful agricultural runoff, as shown by the percentages in Table 1, however, there are key issues regarding if these same removals negatively affect the natural functionality of wetlands.

Table 1: Percentages of Removal and Plant Cover within Global Wetlands

Ecosystem Services Evaluation

The utilization of wetlands for waste treatment cannot be overstated, as it is clear from the research that their ability to remove large quantities of Nitrogen and Phosphorus as well as their potential for pesticide and herbicide removal is of great importance and benefit to the agricultural landscape. However, there are certain key components that should be noted and evaluated in further research including: temperature, seasonality, and pesticide management for denitrification purposes, buffer zones between wetlands and agricultural lands, plant biodiversity, and anthropogenic disturbances.
Denitrification effectiveness is a key aspect to the functionality of wetlands with temperature and dissolved oxygen being the two main components. High flow rates during flooding cause a slowing of denitrification and lack of oxygen into the system, whereas cycles of high water and low water with longer residence times and lower flow rates provide the greatest removal rates (Darwiche-Criado, et al., 2017). The combination of nitrates and pesticides within the system is a challenge for future studies, as certain chemicals (ex. Difenoconazole (fungicide),Deltamethrin (insecticide) and Ethofumesate (herbicide)) in high concentrations (500 mg/kg) have been shown to inhibit denitrifcation processes within the soil (Tournebize, et al., 2017).

Various studies (Buah-Kwofie, et al., 2018; Hayes, et al., 2010) have shown impacts of agricultural chemicals on the biodiversity of the down-stream systems including lakes and rivers. Fish and amphibian species provide a measure of the environmental exposure to the various chemicals due to their uptake structures: fish accumulate chemicals into their tissues and the amphibian’s skin allows for direct assimilation of chemicals via absorption. Fish have been shown to uptake 2-7% of pesticides into their flesh, up to 700% more than the surface soils these chemicals are actually sprayed on and chemicals like atrazine have been linked to the decline of global frog populations (Hayes, et al., 2010).

Mitigation strategies include planting crops that remove excess nitrates and phosphorus (such as corn) for several years between the primary agricultural zones and the wetlands (Ewing, et al., 2012) and planting narrow woodland buffer zones that would break up the flow of water and allow for greater species diversification of animals such as frogs (Sawatzky, et al., 2019). The two CW design methods (in-stream vs. off-stream) can also be utilized to mitigate each type of removal process. In-stream design methods that favor the removal of nitrates can be created where the CW is sufficiently broad allowing for generally equal spread of drainage water over the entire CW. Likewise, off-stream methods can be designed for pesticide removal. This is accomplished by the use of a gate to flood the land after pesticide use and direct the water into the CW. The gate is then closed after a set time allowing for higher residence time of effected waters in the CW (Tournebize, et al., 2017).

Plant biodiversity is another indicator of wetland health and ecosystem functionality. In a comparison between forested, agricultural, and urban wetlands, agricultural wetlands which were semi-permanently flooded with shallow water depth had the most biodiversity of plant species; 81.9% of which were herbs, ferns, or grasses (Moges, et al., 2017). Since plant uptake of N and P have been shown to account for 15-80% of Nitrogen and 24-80% of Phosphorus in the majority of research (Wu, et al., 2015), plant biodiversity and efficiency is of great concern. Anthropogenic factors such as harvesting, grazing, drainage, and waste treatment, while creating microhabitats, also disrupted the natural fauna and allowed for colonizer species which had the biggest effect on species diversification (Moges, et al., 2017). While this is of concern for seriously impaired wetlands, other ecosystem services have to be balanced for the good of the surrounding communities. In addition to aesthetic and recreational uses, many wetlands are used to support agricultural products and if taken into account with the activities, can greatly increase the perceived value of wetlands which may assist in their preservation or management. One such activity is mushroom production on common reed substrate harvested from wetlands.

It has been shown that Oyster Mushrooms grown on a reed substrate produce just as well if not better than on normal wood-shaving substrate and have the added benefit of removing small amounts of Nitrogen (2%), Phosphorus (0.2%), Potassium (1.34%), Pb and Cd from the wetlands through plant uptake (Hultberg, et al., 2018). The additional removal of heavy metals such as Lead (Pb) and Cadmium (Cd) assists with keeping the wetland water clearer for fish and more sensitive plants (Hultberg, et al., 2018). Another reed-focused activity is the creation of cattail (Typhus) pellets for use in wood burning stoves. These pellets have been shown to create between 7,266 and 8.551 BTU/lb which is comparable, if not better, than traditional wood pellets (7,266-7,739 BTU/lb) (Grosshans, et al., 2013) and convert roughly 0.7-0.11% Phosphorus, 0.79-1.53% Nitrogen, and 0.31-0.64% Potassium from the cattail’s dry weight (Grosshans, et al., 2015).

Overall, systems where traditional methods (that is non-fertilizer or chemical amendments) for farming that incorporate low-intensity crop production, grazing, and fish farming where the natural hydrology of the wetlands is left intact, may be the best choice for utilizing wetlands for both ecosystem services as well as economic viability (Verhoeven & Setter, 2010) for the surrounding communities.

Conclusion:

In conclusion, when looking at wetlands and their interaction with agricultural lands, ecology must co-exist with economics, and stakeholder engagement must be high for proper management of ecosystem services as well as economic viability. Wetlands used as landscape elements can benefit from low-intensity anthropogenic disturbances depending on temporal and spatial scales such as seasonality and mitigation efforts. The natural filtration ability of wetlands to remove fertilizers, pesticides and herbicides make constructing wetlands near agricultural lands highly economically viable, yet there are some key aspects of the ecosystem functions and biodiversity aspects that should be reviewed in more detail including the management of biodiversity within the wetlands for the greatest ecosystem service benefits. Overall, the research is clear that wetlands can be used for agricultural drainage treatment, but there is more uncertainty around if treatments negatively impact the very ecosystem services that those agricultural lands are counting on. Incorrect chemical loads and seasonal variability can greatly impact the efficiency of wetlands and should be taken into account when designing or utilizing CWs. The agroecological functionality of wetlands are tied to its hydrology, geomorphology, and biodiversity and these need to be key aspects of evaluation before utilization. 

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