Implementing urban agriculture within the city
boundaries of Amsterdam
Retrieved from: http://www.studiokoning.nl/Foto_17/Zuidas.html
Interdisciplinary Project 2015 Future Planet Studies Supervisor: Crelis Rammelt
Tutor: Jaap Rothuizen Word count: 7215
Boy Luiks Spatial planning 10400095 Marlon Dijkshoorn Ecology 10182500 Marleen van Dusseldorp Earth Sciences 10069534 Marnix Wittebrood Earth Sciences 10449035
Table of Contents
1. Implementing urban agriculture in Amsterdam 4
2. Theoretical framework 6
2.1 Integration visualization 6
3. Methodology
9
3.1 Literature study 9
3.2 GIS/Selecting Soil Sampling 9 3.3 Practical research 9
3.3.1: Setup 9
3.3.1: Lab analysis 10
4. Results for every step in the implementation process 11
4.1 Identification of the problem 11 4.2 Selecting suitable locations 11
4.2.1: Finding suitable land 12
4.2.2: Closing an agreement with the owner 14 4.2.3: Zoning plan 15
4.2.4: Habitat connectivity 15 4.2.5: Site selection 16
4.3 Feasibility of the implementation 17
4.3.1: Improving soil quality - Phytoremediation 17 4.3.2: Experiment soil quality 18
4.4 Predicted consequences of implementation 19 4.4.1: Bee populations 19
4.4.2: Bio control 20
4.4.3: Urban heat island effect 21 4.4.4: Potential production 22
4.4.5: Resilient city 22
4.4.6: Negative consequences 23 4.5 Implementation/conclusion 24
5. Discussion
25
6. Key literature and references 27
7. Appendices
32
Abstract
By using an interdisciplinary approach this research focuses on how to apply urban
agriculture in the city of Amsterdam using existing vacant land in an environmentally friendly manner. Spatial planning will act as an overarching framework, presenting the options for the realization of urban agriculture in Amsterdam. By doing so, the actual implementation of urban agriculture as proposed by earth sciences and ecology will be enabled. This research focuses on the different steps that are necessary to implement urban agriculture in the city of Amsterdam. Firstly, problems that could arise during the implementation of urban agriculture are identified. After this identification, suitable locations for agriculture are selected, taking into account both current policy and ecological connectivity. For these locations the suitability is further determined during the feasibility study: experiments are conducted in order to determine the soil quality and pollutant uptake by vegetation. It is expected that the medium to heavily polluted areas could potentially become suitable for agriculture through the use of phytoremediation. In the last step of the implementation process, both the
ecological consequences and the potential production of urban agriculture are discussed. If closely managed, the positive ecological consequences are expected to outweigh the negative. Furthermore, the potential production of urban agriculture on vacant lots in
Amsterdam is not nearly expected to be enough to provide in its food demand, implying that it will only function as additional food supply.
1.
Implementing urban agriculture in Amsterdam
Global populations are growing and becoming predominantly urban. It is expected that by 2030 more than 60 percent of the global population will live in cities. This trend requires a different approach to how urban inhabitants are being fed (Ackerman et al., 2014). Urban agriculture is increasingly being considered as a solution, by producing food in places where population density is highest, transportation costs can be reduced, inhabitants could become more closely connected to food systems and under-utilized areas can be converted into productive land (Martellozzo et al., 2014). In this research urban agriculture is defined as cultivating, processing and distributing agricultural products within the city boundaries of a large city, such as Amsterdam (Bailkey & Nasr, 2000).
The urbanization trend is expected to continue in Amsterdam as well, leading to a higher population density. Accordingly, it is of importance to reconsider the use of space in the city in order to be able to use every part of to its full potential. For example, rooftops could be converted into suitable areas for cropland and vacant buildings could serve as spaces for hydroponics. In this research we will discuss one specific potential source for the supply of food within the city: converting vacant land into cropland. By doing so, the main following main question will be answered:
How can the city of Amsterdam apply urban agriculture to provide in its fooddemand using existing vacant land in an environmentally friendly manner?
To be able to answer the broad main question, several sub questions are distinguished: - What are the possible places to implement urban agriculture in Amsterdam? - To what extent can these sites be used in within current legislation and policy, and
which stakeholders are involved?
- Are these sites able to support the crop’s growth cycle; to what extent are these polluted or otherwise unusable?
- What is the possible impact of urban agriculture on the ecosystem of Amsterdam? In short, the objective of this study is to investigate the feasibility of implementing urban agriculture in Amsterdam, its consequences for the urban ecosystem and the consequences of soil contamination for the cropland. Vacant land is defined as a piece of land, within the built environment without any manmade structures, that has no function and is not
In order to be able to adequately answer the sub questions and main question, it is necessary to comprehensively address all the steps that have to be completed during the implementation process of urban agriculture. This is the main focus of this interdisciplinary research. The implementation of urban agriculture In Amsterdam is determined by various factors concerning various disciplines. Knowledge from these disciplines will have to be fully integrated in order to assess the implementation comprehensively. For example, in selecting suitable areas for agriculture, knowledge from spatial planning as well as ecological
connectivity is of great importance. In this research, both ecology and earth sciences will examine the optimal conditions for urban agriculture in Amsterdam. Spatial planning will act as an overarching framework, thereby enabling the actual implementation of urban
agriculture as proposed in this research.
The research is structured by presenting the entire food production process, from land preparation to (un)intended consequences. First, it is necessary to describe why urban agriculture is necessary and to identify the problems that could arise during the
implementation of urban agriculture in Amsterdam. Stakeholder debate and soil
contamination in Amsterdam are examples of such problems. Secondly, potential sites have to be selected, taking into account both the current policy and habitat connectivity. The potential urban farming sites equals all the vacant land within the city of Amsterdam where there are no policy restrictions. Ecological connectivity needs to be taken into account in this step to maintain the resilience of the ecosystem. The third step in the implementation
process is to determine the suitability for agriculture based on pollution in urban areas, and assess whether the food is safe for human consumption. As a result of the health risk and the measured concentrations of pollutants in Amsterdam, an experiment is necessary. Soil samples are taken from different vacant sites, which could potentially be converted into cropland. The results of the experiment will demonstrate to what extent the soil is polluted, and to what extent the crops take up this pollution. Fourthly, it is necessary to determine the potential influence of urban agriculture on the urban ecosystem in Amsterdam. An urban area is defined as an area where people live at high densities, and where man-made built structures cover a large portion of land (Martellozzo et al., 2014). In these urban areas, green and blue spaces, including yards and gardens, parks, forests, rivers and ponds are part of the urban ecosystem (Pickett et al., 2001). The urban ecosystem is considered to be a specific type of ecosystem, given that the relations between the actors in this system are severely subjected to human actions (Gómez-Baggethun & Barton, 2012). In this step the implications of urban agriculture for the resilience of Amsterdam and the potential production of the city will also be discussed.
In the last step a brief conclusion will be provided on the current situation regarding the implementation of urban agriculture in Amsterdam.
2.
Theoretical Framework
In order to examine the potential implementation of urban agriculture in Amsterdam, insights of multiple disciplines are needed. These insights can be integrated in an organized
framework of steps that are needed for the implementation of urban agriculture. In short, these steps will go through the entire food production process from land preparation to (un)intended consequences and implementation of urban agriculture. This is visualized by using a combination of ‘system dynamics’ to visualize the process in steps, and ‘value chain analysis’. System dynamics is a methodology to model complex issues and processes and thereby analyse them more easily. It represents the real world in steps moving from a problem to a solution with feedback loop structures. By system dynamics, evaluation of policies and implementation steps can be done in such a way that the process can be understood and improved when necessary (Forrester, 1994). The value chain analysis is more focused on mapping the process view of organizations with inputs and outputs
(Cambridge University, 2013). This value chain analysis is useful when analysing a complete value chain, in this case the supply chain for urban agriculture food. By analysing the
‘chains’ involved (such as stakeholders), the value chain can be improved to increase potential production and decrease negative outcomes (Taylor, 2005). These two methods are used to visualize this research over time (from preparing land to implementation of urban agriculture.), the different actors and disciplines and how they complement each other. 2.1 Integration visualization
Although there are several theories from the three disciplines involved in this research, these theories and insights function as a whole and complement each other as seen in figure 1.
Figure 1: Complementation of the Disciplines Spatial Planning, Ecology, and Earth Science in the research on
In this particular research it is investigated how it is possible to implement urban agriculture in Amsterdam and what the potential positive and negative consequences could be. In order to get a better understanding of this process, each discipline is equally important. This process of implementation and the disciplines involved is described in steps, which can also be seen in figure 2. We distinguish the following steps for the implementation of urban agriculture:
1. Identification of problems surrounding implementation of urban agriculture such as general pollution problems in the city, and the important stakeholders involved. 2. Choosing a specific site, examine characteristics of locations and the policy involved 3. Determine the feasibility of implementation on the specific location, stakeholders
dialogue, experimental outcome for the soil quality and suitable crops, potential habitat connectivity
4. Predict the consequences of implementation 5. Implementing urban agriculture on site
The steps in figure 2 provide the framework in which order this research is conducted, and how this report is ordered. Within this visualization, ‘Input’ and ‘Output’ is marked
transcending the boundaries of the steps. These terms acknowledge the fact that in order to implement urban agriculture on a large-scale input is needed in the form of finances and labour time to do policy research, organize a stakeholder debate and do experiments. However, this input and output will not be further quantified as this research is intended as a framework on how to implement urban agriculture in Amsterdam. When actually
implementing urban agriculture on a large scale, a detailed report should be made on the finances needed.
Figure 2: Integrated Research of implementation of urban agriculture in Amsterdam in five steps (Based on a
3.
Methodology
3.1 Literature study
The core method used during these five implementation steps is a literature study from the different disciplines: Earth Science, Ecology and Spatial Planning. Each discipline gathered means of a literature study in order to describe, summarize, evaluate and clarify the selected area of study, which in this case is the city of Amsterdam (Fink, 2010). During the elaboration of the implementation steps insights from the different disciplines came together and complemented each other, creating an integrative and comprehensive implementation process that transcended the boundaries of the single disciplines.
3.2 GIS / Selection Soil Sampling
As an addition to the literature study, in order to gain insight into the specific places in Amsterdam that are suitable to implement urban agriculture, different data sets (provided online by the municipality of Amsterdam) are analysed using ArcGIS. ArcGIS is a geographic information system (GIS) for working with maps and geographic information. It is a system designed to capture, store, manipulate, analyse, manage, and present all types of spatial or geographical data.
The data sets that are used in the analysis are: Soil Quality and Vacant Space (Gemeente Amsterdam, 2015b). Based on these data sets in combination with an analysis of relevant policy documents the vacant sites in Amsterdam that are suitable for urban agriculture are determined and visualized using GIS. Thereafter, two of these available sites will be selected for the practical research based on soil quality. This concerns an inductive case selection method that results from the second implementation step, and thus will be explained in more detail in that part.
3.3 Practical research
3.3.1: Setup
As part of the feasibility assessment of urban agriculture on specific sites and to look into the uptake of pollutants by crops, an experiment was conducted using soil samples collected in Amsterdam to test the growth of crops in urban conditions. This experiment is meant as a proof of concept, and not as a full experiment into the many possibilities of urban agriculture, since time was a very limiting factor. The samples were collected from two randomly
selected sites in Amsterdam, as explained in the second implementation step (paragraph 4.2).
The soil samples were collected from several different points on the plot, to make sure the sample represented an accurate representation of the site.
Three pots were used for every sample, which resulted in nine pots total being used: three pots were filled with potting soil as a control group, three pots were filled with soil collected from site X and the last three pots were filled with soil collected at site Y. Part of the sampled soil was set aside and analysed on the existence of several contaminants. Then three sugarcane maize seeds were placed in each pot. Sweet corn was selected for this
experiment based on previous experience with the plant, and its relatively high growth rate. Multiple seeds were put in each pot to increase the likelihood that at least one would grow.
In follow-up experiments, it is advised to use several types of food crops, preferably those that have high levels of consumption in society, but this was not an option for this experiment because of time constraints.
The pots were then placed in the greenhouse and watered twice a week, making sure the soil was kept moist throughout.
Measurements of the plants were taken at 2 and 4 weeks into the experiments to keep track of the relative growth of the plants.
After 4 weeks, the plants were harvested and analysed in the lab.
3.3.2: Lab analysis
For the lab analysis, some pre-treatment of the soil and plant samples was needed: 1) Dry the samples for 72 hours on 40 *C
2) Sieve and grind the samples to <0.2 mm
3) Weigh 250mg of the sample material of each sample
4) Add 4,0 ml HNO3 65% and 1,0 ml HCl 37% and let it rest for 60 minutes 5) Add 1 ml H2O and put the samples in an USER004 microwave
6) Transfuse the mixture in a 50ml flask, add demiwater to the 50ml line
After this preparation, metals will be measured with an AAS spectrometer (Kingston et al., 1997).
4.
Results for every step in the implementation process
4.1 Identification of problemsIn 2050, it is expected that the current global population size will have doubled due to exponential population growth. Moreover, this expanding population will increasingly settle in urban areas: it is expected that by 2030 60 percent of the global population will live in cities (Ackerman et al., 2014). As a result of the ability to preserve food and transport it over long distances enables cities to expand rapidly, without the supply and presence of food being a limiting factor (Steel, 2008).
While the number of urban inhabitants will continue to grow, these residents are
predominantly dependent on rural food production. Currently, urban areas are already using 75 percent of the earth’s resources, leading to degradation of the rural landscape (Steel, 2008). As a result of these tendencies, a different approach to feeding urban inhabitants is needed. Growing food locally could contribute to reducing the environmental impact of food production. For example, under-utilized areas could be converted into cropland,
transportation emissions and costs could be reduced and urban residents could become more closely connected to food systems and their natural environment.
When implementing urban agriculture in Amsterdam, it is to be expected that several
problems will arise which have to be overcome. A significant problem is the considerable soil contamination in the city of Amsterdam. Due to the high presence of arsenic in the soil and groundwater of Amsterdam, it is necessary to specify the effects of this polluted soil on crop growth. Conducting an experiment will assess the health risks of eating these locally grown crops. Other problems, concerning the implementation, that are dealt with in this report are stakeholder debates during site selection and potential negative ecological effects of urban agriculture.
4.2 Selecting suitable locations
Currently, the municipality of Amsterdam has no specific policy on urban agriculture. There is no central body that is particularly concerned with urban agriculture, and the districts differ organisationally (CITIES, 2011). Due to the current economic conditions many real estate project have been cancelled or temporarily put, which provides space for temporary urban agriculture projects. All the vacant land in the city is in fact available for various initiatives, under which urban agriculture. The different districts do stimulate urban agriculture as they mostly give permission to start these initiatives (Gemeente Amsterdam, 2013). When starting an urban agricultural project various procedural aspects should be taken into
we will also present the total amount of vacant land in Amsterdam that is available for urban agriculture. Finally, two sites are selected for the practical research.
4.2.1: Finding suitable land
The first thing to do when starting an urban agriculture initiative is to find a suitable location. By looking at the quality of the soil the vacant sites in Amsterdam that are available for urban agriculture activities will be determined. With the Nota Bodembeheer (2013) the municipality of Amsterdam sets a policy framework for dealing with vacant land and soil pollution. For both health and agricultural reasons it is important that soil used for urban agriculture is of a certain quality. The municipality of Amsterdam distinguishes six different zones based on average soil quality (Table 1). This average soil quality is divided into four classes, from least to most polluted:‘Achtergrondwaarde’, ‘Wonen’, ’Industrie’ and ‘>Industrie’ (Gemeente Amsterdam, 2013).
Table 1: Soil quality zones with functions and average soil quality (Gemeente Amsterdam, 2013)
Figure 3 shows both the spatial distribution of vacant land in Amsterdam, as well as the soil quality divided into the six zones that are mentioned in Table 1. Also included in this analysis are remediation areas. As a result of the differences in soil quality not all the vacant land presented below is suitable for urban agriculture activities. The municipality of Amsterdam has determined Local Maximum Values (Lokale Maximale Waarden) for different substances that can be present in soils (Table 2). These values depend on the function of the soil. The more sensitive the function, the higher the maximum values (Gemeente Amsterdam, 2013).
Figure 3: All vacant land in Amsterdam projected over the soil quality zones (GIS, based on data from the
municipality of Amsterdam, 2015b)
As can be seen in Table 2 services such as agriculture and vegetable gardens are only allowed for Local Maximum Values, which belong to the soil quality classes
‘Achtergrondwaarde’ and ’Wonen’. Thus, according to table 1, urban agriculture is only
available on sites within zone 1 and zone 2.
This is incorporated in figure 4, which shows vacant land that lies within areas that are suitable for urban agriculture, namely zone 1 & 2. In total, 1.207.655 m2 of vacant land is
available for urban agriculture. Especially in the city centre the areas are unsuitable for urban agriculture as a result of soil pollution. Still, the majority of the sites can be used for urban agriculture. The vacant lots that lie in remediation areas are also considered available for urban agriculture, as it is expected that after these remediation efforts the soil quality is good enough for such activities.
Figure 4: Vacant sites in Amsterdam which are suitable for urban agriculture (GIS, based on data from the
municipality of Amsterdam, 2015b).
4.2.2: Closing an agreement with the owner
After a suitable piece of land is found the next thing to do is to contact the owner and discuss future plans. Generally, the municipality of Amsterdam, housing associations, project
developers or private individuals owns vacant land. In Amsterdam the municipality has stopped selling land, and now gives out land on leasehold. By paying a fee, the leaseholder
has full right to the land (CITIES, 2011). It is important to arrive at a clear agreement with the owner with regard to the proposed actives and the duration of use. CITIES (2011) state that such an agreement must guarantee the rights of the user, while at the same time assures that the owner can use the land for other purposes after the agreed time. The latter is often a requirement for owners to allow temporary use. In practice it appears that there are often difficulties in reaching optimal agreements with owners of vacant land.
4.2.3: Zoning plan
After an agreement is made with the owner of the vacant piece of land, the zoning plan has to be respected too. In the report of CITIES (2011) it is stated that in this part initiators often experience bottlenecks such as strict hygiene rules and strict zoning laws. However, when agricultural activities are not in line with this zoning plan, the district administration may authorise to deviate from this plan for a maximum period of five years. The ‘Omgevingswet’, which will probably enter into force in 2018, offers more flexibility so that urban agriculture can be incorporated into spatial plans more easily.
4.2.4: Habitat connectivity
When determining suitable locations for urban agriculture in Amsterdam, the ecological resilience of the urban ecosystem needs to be taken into account too. Habitat connectivity is of great importance for this ecological resilience: gene flow can be maintained and
ecological fitness will strengthen as a result of this connectivity (Savada et al., 2008).
Fragmentation of the vegetative surface can disturb ecosystem processes, reduce gene flow and cause erosion of genetic variation (Young et al., 1996). Habitat fragmentation leads to extinction rates attributed to chance increasing.
Natural fluctuations in population size and fitness traits are not a problem in large populations, but in smaller populations a buffer is not present. A negative mutation can spread through a small population much quicker because there is less genetic variation, leading the mutation to become fixed in the population (Lienert, 2004).
Natural hazards are also more likely to affect fragmented populations compared to large connected populations. In large populations with habitat connectivity the probability of going extinct due to natural hazards is much smaller. This is a result of natural chance as well as a more diverse natural environment, in which migration is possible (Lienert, 2004).
It is strongly advised to take habitat connectivity into consideration when planning urban agriculture. Areas designated as “ecologische hoofdstructuur” (as seen in figure 5) should be considered as primary candidates for urban agriculture.
Figure 5: Ecological structure as proposed by the municipality of Amsterdam. The red crosses are bottlenecks
that have to be removed, the bigger the cross the higher the priority. The proposal was made in 2012 and is expected to be complete in 2040 (Gemeente Amsterdam, 2012)
4.2.5: Site selection
Soil samples were taken for practical analysis from two different locations in Amsterdam: Amsterdam Business Park Osdorp and Zeeburgereiland (Sluisbuurt). The first is located in zone 1, and the latter in a remediation area. These locations were chosen specifically because they have different soil quality, and therefore it can be determined whether this will affect the uptake of contaminants and the growing of the crops. However, these sites are still located in areas that are suitable for urban agriculture. The remediation area can be
considered as an area in which phytoremediation could be applied, as it is not remediated yet and more pollutants are present. In figure 4 the chosen sites are circled in red.
Amsterdam Business Park Osdorp
The vacant site Amsterdam Business Park Osdorp is located in Nieuw-West. The site has a size of 110000 square meters and is owned by the municipality of Amsterdam (district Nieuw-West). The municipality stated that they are actually looking for a permanent function, but that under strict conditions is a temporary filling is possible.
Zeeburgereiland (Sluisbuurt)
The vacant site Zeeburgereiland is located in the eastern part of Amsterdam, and covers a total area of 270000 square meters. The owner of the site is the municipality of Amsterdam, who has no requirements regarding the function and the duration of use.
4.3 Feasibility of the implementation
In Amsterdam, the soil is polluted in most places. The houses in the city centre are built on an embankment layer that is polluted by centuries of industrial activities and dumping of city waste. Consequently, there are health risks when crops produced on this soil are eaten regularly. To make sure that urban agriculture does not provide a health risk, soil research needs to be done. Next to the soil pollution itself, another important aspect of agriculture in the city is the question to what extent the plants take up this pollution. The municipality of Amsterdam (Gemeente Amsterdam, 2015a) states there is a big difference between different types of plants. Leaf and root crops take up more substances from the ground than fruits growing on trees. Vegetables growing close to the soil are at greater risk of contamination, since the further away the edible part from the soil, the less risk it has of taking up pollutants (Lenntech, 2015).
4.3.1: Improving soil quality - Phytoremediation
One way to improve soil quality, and remove pollutants, is by employing phytoremediation. Phytoremediation uses plants, instead of chemicals or other methods, to remove these contaminants from the soil.
Phytoremediation is divided into several different areas, namely: phytoextraction,
phytodegredation, rhizofiltration, phytostabilization, phytovolatilization and the use of plants to remove pollutants from the air. For improving urban soils phytoextraction is most
appliable, which is the use of pollutant accumulating plants to remove metals or organics from soil by concentrating them in harvestable parts, although phytovolatilization is also a potential candidate of interest (Salt, Smith and Raskin, 1998). Phytovolatilization increases the volatility of certain pollutants, meaning they can start moving through the soil. Combined with phytoextraction, this could lead to increased uptake of pollutants.
There are two types of phytoextraction, one that uses chelates (substances that can create several bonds with metal ions) to increase bioaccumulation of the metal, and one that uses hyperaccumulator (plants to grow well on soils with large amounts of metal present). Hyperaccumulation has been studied from as early as the 1880s, when a German botanist discovered plants that grew on zinc rich soil had large concentrations of zinc in their leaves (Salt, Smith and Raskin, 1998). Phytoremediation has already been used to effectively and efficiently clean arsenic (Pilon-Smits, 2005).
Phytoremediation used to be viewed as a cost ineffective way of removing
contaminants only a few decades ago (Chaney, Malik et al., 1997). Since then, this view has come around, and phytoremediation is now viewed as a cost effective and efficient way to remove pollutants from soils (Pilon-Smits, 2005;, Regier, 2007).
In the implementation process, it is necessary to assess the health risks of eating vegetables grown in Amsterdam, and to determine the potential of phytoremediation to take up soil pollutants. Therefore, the experiment explained in the methods is conducted to estimate if urban agriculture could be implemented directly on these two sites, or that phytoremediation should be used first to reduce pollution concentrations in the soils.
4.3.2: Experiment soil quality
From the AAS spectrometer, the results per soil sample and plant sample are given in figure 5.
Figure 6: Results of the AAS spectrometer measurements on four metals: As, Zn, Pb, and Cu for the three soil
samples and the plants grown on these soil samples
The aspects that are immediately stand out in figure 6 are the levels of zinc contamination in the plants in the control pot, as well as in the Zeeburgereiland plants. Secondly, it is
noticeable that the values for all chemical concentrations are extremely high. For instance, the acute lethal dose for arsenic is around 70 to 200 mg (Dart, 2004). From this it can be concluded that the values presented in the graph are too high. Sadly, this means no
absolute conclusions can be drawn from the values, but since they were all measured in the same way, they still hold relative values to each other.
As can be clearly seen in figure 5, the zinc contamination in Zeeburgereiland is higher than in the other soils. Other than that, all the soils seem to have all the contaminants in the same range, meaning the Osdorp soil is as polluted as the control soil used.
The maize plants also appear to have an affinity for zinc, showing high uptake across the board, even in the soils with lower amounts of zinc present, except for in Osdorp. This looks like a deviation from the other two.
Also of note is the fact that the plants have far higher values than the soils. Since the same techniques were used to extract the metals and measure the samples, it seems unlikely that the plants have extracted almost all of the metals from the soil in the short 4 weeks they were allowed to grow. One potential explanation for this would be that the soil and plant samples were accidentally swapped, meaning that the soil values are actually the values for the plants, and vice versa.
4.4 Potential project outcome
Before implementing urban agriculture, it is important to have a look at the potential consequences implementation might have. Since (potentially) new plants species are introduced, urban agriculture can affect many different things. For instance, it could have an impact on bee populations in the city, it could improve biodiversity, and it could help
strengthen current habitat connectivity in the city (Young et al., 1996). Moreover,
implementation could also have effects on a larger scale, such as influencing the amount of heat coming off a city (a so-called urban heat island) (Wolters et al., 2011).
Important to note is that urban agriculture does not necessarily need to affect the city in purely positive ways, it is very possible that the city finds itself negatively affected in some areas.
Furthermore, the consequences that will be mentioned here are by no means an exhaustive list. It is very well possible that other effects of urban agriculture are present, and these might not have been documented yet.
4.4.1: Bee populations
Bee populations have seen a vast decline over recent years (Giannini et al., 2012), yet they are very important for some agricultural fields. An increased bee population in Amsterdam could potentially positively contribute to its crop production since a variety of crops can produce higher and more stabilized yields when pollinated by insects. For example, cucumbers, squashes, peppers and cauliflowers benefit from pollination (Matteson et al.,
2010). Some of these vegetables are capable of self-pollination, but the yields of these crops will be enhanced by available pollinators (Klein et al., 2007).
No research was found to support that urban agriculture helps bee populations, but no literature was found claiming that it negatively affected bee populations either. However, research has shown that a wide diversity of flowering plant species can greatly influence bee species richness and abundance (Giannini et al., 2012). Since bees are very important for some crops, the municipality of Amsterdam could improve the diversity of flowering species in the city and could set incentives resulting in more people willing to improve habitat quality for bee populations.
4.4.2: Biocontrol
Biocontrol, or biological pest control, is an important part of functioning urban agriculture, since it reduces the need for pesticides and herbicides, which could be a health hazard for the surrounding city.
It was found that particularly in vacant lots, biocontrol activity is high. In these vacant lots ants especially were found to contribute to a majority of the biocontrol services. To help expand the biocontrol already present, implementing urban agriculture on vacant lots in Amsterdam would be suitable as a foundation for building a sustainable biocontrol network (Yadav et al. 2012; Lin et al., 2015).
Besides microbes and invertebrates, arthropods are also capable of performing natural pest suppression. Therefore they are considered to be an important biotic component of the urban ecosystem. These organisms reduce damage of herbivores to vegetable and fruit crops, and also urban trees and ornamental landscape planting can benefit from the
arthropods. Arthropod abundance is best explained by flowering diversity. This suggests that a flowering diversity is not only beneficial to preserve and stimulate bee population, but also supports arthropods. Accordingly, growing a wide number of different crops and other flowering species in Amsterdam could promote this natural pest suppressor (Bennett et al., 2011). This was also concluded in the research done by Crossley et al. (1992), who
mentions polyculture as a positivie influence on species diversity (figure 7). In addition, this research concluded that that minimizing the use of pesticides can promote natural pest control by arthropods as well as invertebrates and microbes living in the soil.
Figure 7: Changes in species diversity of arthropods as a function of agricultural practice. (Reprinted from
Crossley et al., 1992)
4.4.3: Urban heat island effect
In the urban ecosystem artificial impermeable surfaces, such as concrete and asphalt, cover a significantly more extensive area than in rural areas. These artificial impermeable
structures result in a darker surface area, which leads to a reduced albedo in cities.
Accordingly, radiation is stored more effectively and a specific local climate will arise within urban areas. Radiation stored in impermeable surfaces is slowly released as long-wave radiation during the night (van Hove et al., 2014). This local urban climate is described as the urban heat island effect, a theory that was first described in 1818 by Luke Howard (Howard, 1818). Besides radiation being stored more effectively, wind patterns are altered as a result of artificial structures built in city centres. In addition, evapotranspiration is significantly reduced in comparison to rural areas. This is due to the large percentage of impermeable surfaces in urban areas, which ensures precipitation to be drained effectively. This results in less evaporation in urban areas, while evaporation has the ability to extract heat from the surface area (Wolters et al., 2011).
While perhaps not a immediately noticeable effect, by introducing urban agriculture within the city boundaries, the urban heat island effect can be mitigated. By implementing urban agriculture on vacant lots, the albedo of the urban surface could increase, positively altering radiation uptake in Amsterdam (Grewal et al., 2011; Zinzi & Agnoli, 2012). Furthermore, the
implementation of urban agriculture could potentially increase evaporation, resulting in an increased release of heat from the surface.
Mitigation of the urban heat island effect could have positive effects for both the comfort levels of urban communities and diminishing the energy use for cooling (Lin et al., 2015). According to Wolters et al. (2011) the heat island effect in Amsterdam is estimated to cause a temperature rise of 7,8 °C. Reducing this temperature rise could create different growing conditions for vegetation, possibly resulting in an altered vegetation structure in Amsterdam.
4.4.4: Potential production
Martellozzo et.al. (2014) have studied the potential production of urban agriculture on a global scale. They developed a theory of estimating for each country the part of total urban area that is needed to meet the consumption target. According to Martellozzo et al. (2014), when looking at the recommended consumption of vegetables, 10-25 % of the total urban area in the Netherlands is needed to meet this consumption. If we assume that every city in the Netherlands will provide relatively the same amount of urban land for urban agriculture practices, this means that also 10-25 % of the total urban area of Amsterdam must be used for agriculture. The city of Amsterdam has a total surface area of 219,32 km2, of which 53,56 km2 water. Thus, the total amount of vacant land that is suitable for urban agriculture in Amsterdam is 0,73%1 of the total urban area in Amsterdam. This does not even come close
to the percentage that is needed to meet the recommended consumption target, also because this number assumes that all vacant land will be used for urban agriculture purposes, which is highly unlikely. However, this analysis does not include other potential places for urban agriculture such as buildings (vacant office spaces) and public space.
4.4.5: Resilient city
As explained in the appendix a city can become more resilient to external influences when it is more self-sustaining. However, it is calculated that only a small percentage of the total outside urban area of Amsterdam can be used for urban agriculture. This would be not enough to make Amsterdam self-sustaining. However less import of foods would be needed, and thus less CO2 output from transportation is needed (Seeliger, 2013). Also, not all potential production places are included in this research. One example is the potential production in vacant indoor places in Amsterdam including empty offices, while a lot of research is done to indoor farming like vertical farming and hydroponics using LED light systems (Yeh & Chung, 2009).
Another potential place for production that is not incorporated is on roofs of buildings, which is also an upcoming experimental place for growing food (Whittinghill & Rowe, 2012). When
combining these potential production places, including urban agriculture on vacant land, Amsterdam could be more self-sustaining in its vegetable and fruit demand.
4.4.6: Negative consequences
As mentioned, not all consequences of the implementation of urban agriculture will be positive. This report will attempt to highlight some of the potential negative effects as well. Disease transmission
Disease transmission from crops to other natural systems and humans could both be a potential danger. Examples of urban agriculture providing a breeding site for disease-transmitting insects have been described, although it is rather unlikely that this would happen in a controlled environment in the city of Amsterdam (Lin et al., 2015).
Chemical spill over
The spill over of chemicals into the natural system, leading to environmental pollution and possible health risks have also been described. According to Lin et al. (2015) this potential danger is of importance in non-organic urban agriculture, which is why the aim of this
research is to implement urban agriculture in an environmentally friendly way. Stimulation of biocontrol, for example promoting arthropod species and invertebrates and microbes in the soil, is of major importance. By doing so, the use of chemicals for pest control is minimized and organic agriculture could be realised (Braaker et al., 2014).
Invasive species
Planting exotic breeds alongside of native breeds could have a positive effect for the vegetative diversity and overall biodiversity in Amsterdam. However, these exotic breeds could potentially outcompete biota already present in the urban area. A species that outcompetes native biota is called an invasive species. Occasionally exotic plant species become invasive species due to the lack of natural enemies in the new environment, or due to their adaptation to specific climatic variables (Lin et al., 2015). These invasive species would have the ability to outcompete other crops as well as other plants species in natural parts of the city of Amsterdam. This implicates that information about the characteristics of exotic crops is needed prior to planting them.
4.5 Implementation/Conclusion
In conclusion, urban agriculture could have several positive consequences for the urban ecology of Amsterdam. Biodiversity could be enhanced and arthropod species, invertebrates and microbes could provide biocontrol services. Additionally, crop growth is likely to
positively influence the growth of bee populations and mitigate the urban heat island effect. However, several preconditions underlie these positive results. Habitat connectivity should be promoted and flowering diversity should be maximized, taking into account the invasive species effect. If closely managed, the positive impact of crop growth outweighs its negative consequences.
Currently, the city of Amsterdam has no specific policy on urban agriculture. There is no central body of the municipality of Amsterdam that is particularly concerned with urban agriculture, and the districts differ organisationally. The vacant lots in the city are available for (temporary) initiatives including urban agriculture, whereas the different districts are generally positive about urban agriculture and promote such initiatives. When initiating such projects it is important to contact the local district at an early stage of the process. Then, when a suitable piece of land is found, it is important to find out who owns it and what the future plans are. Furthermore, a soil research needs to be done, and a clear agreement with the owner of the land has to be made, regarding the specific activities and the duration of use. The zoning plans are to be respected too. When agricultural activities do not fit into current zoning plans, the district administration may give the authorization to temporarily deviate from the plan. This exemption may be granted for a maximum period of five years. If using treatment for heavily contaminated soils, and carefully selecting plant species on lesser-contaminated sites, it is possible to implement urban agriculture in Amsterdam in an environmentally friendly manner.
By using phytoremediation, heavily contaminated areas can be cleaned and prepared for urban agriculture, and by selecting resistant species of food crops, the uptake of pollutants can be minimized on the lesser-polluted sites.
5.
Discussion
The experiment was set up as described because of time constraints. If more time was available, the setup would’ve been broader, including: samples from more sites, different plants, more sample pots, etc.
These are all things that should be addressed in further experiments. We would like to make the following suggestions for any follow-up experiments.
- Give the plants more time to develop so it’s crops can be analysed;
- Examine the potential for the most popular crops that are eaten in the city where urban agriculture is planned to be implemented, and plan the experiment according to these species;
- Look into the most prominent contamination sources and pollutants, and select species based on resistance or hyperaccumulation, so that either the contamination can be removed or is not an issue when farming these crops.
When agriculture will be implemented in Amsterdam, looking into the preferences of consumers in the city is necessary to prevent oversupply. While fulfilling the consumption patterns of these citizens, it is also necessary to take into account the ecological
consequences of this specific crop growth. For example, in the Netherlands the vegetables that are mostly bought are lettuce, cucumber and tomato. It would be efficient to just grow these core-vegetables using urban agriculture, because it would take into account the needs of a lot of citizens. However, this would not fit the ecological optimum using a wide variety of different flowering species to increase biocontrol and potentially stimulate the bee
population.
Moreover, it should be noted that implementing urban agriculture in Amsterdam is not the optimal way to realize habitat connectivity or to improve the resilience of the urban
ecosystem. Urban agriculture will be implemented in order to contribute to providing in the food demand of Amsterdam, and has some positive influences on the urban ecology. When converting the vacant land solely to improve the ecosystem resilience and to strengthen its ecosystem services, growing crops would not be the best option. Increasing tree cover and planting specific vegetation in order to improve the bee population would be a better way to improve the ecosystem as a whole. However, by implementing urban agriculture outside on vacant lots and not only inside using hydroponics, the ecosystem will benefit in different ways described in this report.
In this paper we argue that less than 1% of the total surface area of Amsterdam is suitable for urban agriculture, where 10-25% of the surface is necessary in order to meet the demand
for food in the future. However, it should be noted that this calculation does not include other potential places for urban agriculture such as buildings (vacant office spaces), roofs and public space. This means that the actual percentage of the surface area of Amsterdam that could possibly be used for urban agriculture is higher. Furthermore, techniques (i.e.
hydrophonics, and LED lights) to grow food in buildings are likely to have a high potential output (Yeh & Chung, 2009). Thus, overall, it is expected that the potential production of urban agriculture in Amsterdam is high enough to make Amsterdam self-sufficient in terms of fruit and vegetables.
Finally, in this paper the implementation of urban agriculture is presented as a rather linear process. However, according to the theory of system dynamics so-called feedback loops may occur when the outcome of the implementation process influence input sources. When using the implementation process for urban agriculture again, especially the feedback link between output and policy should be taken into account. For example, new policies could more thoroughly take into account the role that biotic components will eventually have on reaching self-sufficiency in the city of Amsterdam.
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7.1 Appendix A: Data Management Tables
Discipline or Subdiscipline
Name Theory Key concepts Underlying
assumptions
Insights into the problem Spatial Planning Tactical
Urbanism Urban Transformation Temporary Use Brownfield Development Temporary use of vacant land in the form of urban agriculture Possible vacant sites available for UA
Spatial Planning Local food system planning
Local planning agency can play an important role in planning for an improved food system Top-down approach urban agriculture can be stimulated by local (food) policies Spatial Planning Environmental
Policy Integration A way to consider urban agriculture in spatial policy and planning Spatial Planning/ Economy/ Agriculture Potential Production urban agriculture, urban land use, food security, Potential production depends on available Shows how much land is needed to meet
global vegetable demand area required land demand Earth Sciences/ Agriculture urban agriculture urban agriculture, economic activities, destination, location, products, areas, scale urban agriculture involves many disciplines Shows how many dimensions are involved in urban agriculture
Earth Sciences Soil quality Soil quality,
organic matter, infiltration, aggregation, ph, microbial biomass, bulk density, topsoil depth, conductivity Soil quality involves more than measuring one parameter Provides a way to do estimate the state of the soil, and how to do soil research Earth Sciences/ Geography
Resilient City Resilient cities,
urban resilience, adaption to climate change, transition towns, sustainability Resilient Cities need to be flexible, and therefore make transitions Shows that urban agriculture can help make a city more resilient
Earth Sciences Availability of
nutrients in soils Mobility of Nutrients Nutrients are mobile how nutrient uptake through plants is realized Earth Sciences /Biology uptake of arsenic by plants Uptake of nutrients by plants Plants don’t just take up nutrients Provides a way to tell how plants
from the soil, they also take up contaminant s. Some of these are toxic for the plant itself react to contaminant s in the soil, and how much ends up in the plant itself
Interdisciplinary Green Urbanism Zero waste, zero emission urbanism Zero-waste Zero-emission Overarching theory for the research report Earth Sciences, Biology, Ecology Phytoremediatio n Plants used to remove pollutants from soil Plant nutrient and pollutant uptake Provides a way to clean a polluted site of arsenics and other pollutants Ecosystem dynamics Food web theory
Food chain Every food
web is based on primary producers. Every organism needs a food source (input) to be able to survive. combined overview of every food chain in an ecosystem. Ecosystem dynamics Population ecology Species populations, Species, Systems thinking In an ecosystem various components exist changes in a system lead to a reaction of this system. In
together in an equilibrium. When one aspect of the ecosystem changes, a new equilibrium has to be found. Other organisms react. population ecology species population dynamics and their interaction with their environment is described. Ecosystem dynamics
Invasive species Exotic, Outcompete species that is not native (exotic) to the environment and outcompete s the native species. Social sciences / ecology Metabolic rift theory Rift Capitalism is the driving force behind urbanism. the disruption between humans and their natural environment , caused by capitalism and its effects.
services environment interaction depend on ecosystems for long-term conditions of life (health, security, social relations) (Gómez et al., 2012) humans obtain from ecosystem functions (De Groot et al, 2002).
Ecology Heat island
effect: Metropolitan area, Evapotranspirati on Winds are weak due to buildings. More impermeable surface increase heat-intake. Store more radiation. metropolitan area is significantly warmer compared to rural areas.
