Greener cities through Tile Taxing

People do not often consider cities to be an ecosystem. Yet when I saw a hedgehog rummage around the streets of city-center Amsterdam I realised that that really is what a city is, not unlike a dune area or a forest. A collection of flora and fauna delicately balanced and living off each other and with each other. A city is, perhaps, an entirely man-made ecosystem, in which we have control over even the smallest of details. Is it, then, not strange that we treat a city vastly different from a forest. Plants and trees have value and so do animals, not only for recreation, but also for productivity and regulation of extremes. All around the world we are noticing that urban areas are struggling with pests, heatwaves and floods. It is widely accepted by policymakers that vegetation, greenery and parks will counteract many of these problems. There is, however, difficulty in this as building more parks takes up a lot of space and would require tearing down many (monumental) residential buildings. For cities like Amsterdam, however, there could be an easy solution. It should become common policy in Dutch cities that 60% of back- and front-yards should be covered in vegetation. There are a number of great advantages to such a “tile taxing”, I will discuss these concisely. 

Decreasing urban heat islands

 Urban heat islands are caused by the heat uptake retention of concrete and other building materials to a much greater extent than for example water or vegetation. These urban heat islands account for sometimes up to a few degrees extra warming in certain areas of cities, causing higher risk of strokes and other health hazards, especially to the vulnerable parts of the population such as the elderly, disabled and young children. Parks have been shown to decrease the urban heat island effect and even a singular tree already makes a difference. They do this not only by providing shade, which is a more minor factor than one may expect, but also by less heat uptake and increased heat regulation through evaporation of moisture that was present in the vegetation. If tiles would be replaced by vegetation in all backyards it would create a similar effect. 

The effect of Urban Heat Island (UHI) 
Urban Heat Island Effect. Source: https://www.researchgate.net/figure/The-effect-of-Urban-Heat-Island-UHI_fig1_326316773

Retention basins for Heavy rainfall and drought

Flooding due to heavy rainfall already occurs a few times each year and in future climate scenarios this will only become worse. Weather extremes will become more frequent and both drought and heavy precipitation events will become less exception and more the rule each summer. This leads to great challenges in future city planning where heavier precipitation events may cause serious harm to infrastructure and people if flooding would occur regularly. One effective way to counteract flooding is to build retention basins. Retention basins are designated areas that can absorb water and delay the time it takes the water to reach the sewage system. Something that functions brilliantly as retention basins are parks and vegetation covered gardens. The plants ensure more initial evapotranspiration, causing a lower influx of rainwater and delay the time it takes the water to reach the surface. Once the water has arrived here it is partly soaked up by the soil and retained there. This process greatly reduces the stress on the sewage system and damages on infrastructure due to flooding. In case of drought quite the opposite occurs where the foliage cover reduces evapotranspiration causing more water to be retained in the soil. As well as the vegetation providing the cooling mentioned earlier.

How Rain Gardens Work
Retention basins through vegetation. Source: https://www.romi.gov/1333/How-Rain-Gardens-Work

Increased biodiversity

Biodiversity is often relatively low in cities. However, indigenous species such as hedgehogs, hares and foxes, as well as smaller species such as frogs, toads and newt could easily return to urban areas if larger portions were covered in vegetation. Not to mention insects (notably bees) and birds. This would not only help control pests such as mosquitoes, flies and mice but would also increase overall human happiness. As it has been shown that being exposed to nature increases happiness in people. 

Intelligent Tinkering” - How to Boost Biodiversity at Home ...
Garden Biodiversity. Source: https://www.firstlighthabitats.com/blog/intelligent-tinkering-leopolds-wise-words-part-2

Discussion and conclusion

Apart from the aforementioned reasons to ensure more greenery in urban gardens some other things include improved production, as company buildings next to parks are shown to be 10% more productive than those not exposed to vegetation. And increased real estate prices, since property in greener (yet otherwise identical) areas is more valuable.

Arguments against tile taxing would be that it would be too time consuming for some hard-working people to take care of a green garden and that tiling a garden reduces maintenance cost and time. Solutions to this can be found however, both in community- and municipality-provided aid. The possibility of exemption in case of inability and education on low-effort green gardens that require little maintenance, but function nonetheless.  

Tile Taxing would reap a great many benefits and aid in climate-proofing cities for the future. While keeping a garden green and flourishing may require some effort of people who do not have the time or do not wish to put in the effort, it is of great importance to cities to ensure that there is enough vegetation cover. And solutions to this problem can easily be found through aid, exemption or education. While there are still some practical issues that need to be resolved such as the occasion of smaller backyards that are used as storage for bikes or other materials, solutions to this are easily introduced.

Additional reading:

KWR 2014: Risico’s van klimaatverandering voor de drinkwatersector

KNMI’14-klimaatscenario’s http://www.klimaatscenarios.nl/brochures/images/Brochure_KNMI14_NL_2015.pdf

Enhancing Resilience of urban ecosystems through green infrastructure

https://oppla.eu/groups/enroute

9 thoughts on “Greener cities through Tile Taxing

  1. Interesting topic! What do you think about the potential of green roofs? I think many people who live in Dutch cities don’t have a garden. Should there also be a tax for people with a roof that would be suitable to transform into a green roof? Or would that be too expensive to include in common Dutch policy?

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  2. I really enjoyed reading your post, it made me realise that having natural environments in our vicinity is invaluable, in even more ways than I thought. One barrier I could see for implementing this though, is that I expect many people, including politicians, will be hesitant about setting up yet another tax. I agree that to obtain widespread progress with this easily, something like a tax would work well, but I’m afraid there would be significant resistance from people believing the government is yet again forcing its will on them through taxation. I could see information and education about the benenificial effects of extra greenery taking away some of this, but I’d expect resistance nonetheless. What do you think about the viability of such policy? Maybe there are other ways to increase support, such as running trials first on the local level?

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  3. Thanks for the interesting post! I was wondering about the same question as @bramauc, namely, how can you create enough incentive for people to go through with changing their gardens? Maybe subsidies for people who do increase the amount of vegetation in their garden could offer some kind of solution. The main issue I see here is that this would require money from the government, which may be difficult to come by. Therefore an in-between solution, with some kind of tile tax in place from which revenue is used to subsidize, may be in order. By creating both positive and negative incentives, the “forcing of the government’s will” effect can be reduced, though some government expenditure would likely still be necessary. The same kind of situation could be applied to green roofs/balconies, etc.

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  4. @jobtalkswater2020 I agree on the fact that vegetation provides enhanced heat regulation via evaporation. But wouldn’t this also mean that an increase in vegetation would increase the humidity during such heatwaves (which increases the health risks)?

    I agree with @jaspstevens that subsidies will probably work better than a tax. I don’t think there is an issue for municipalities subsidizing more vegetation, since it has a lot of benefits for the city as mentioned in this post.
    Another possible solution to increase the vegetation coverage is including conditions for backyards in contracts when renting or buying a house. Or require that buildings from housing associations have “green roofs”.

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  5. Very interesting thank you! I would be very interested in seeing this idea take off in the United States. The big, green, manicured lawn is very much the norm in the US, especially in the suburbs. American grass lawns cover 50 million acres and consume 3 trillion gallons of water a year (see https://www.nrdc.org/stories/more-sustainable-and-beautiful-alternatives-grass-lawn). I’m not sure if a tax would be politically feasible as some of the other commenters suggested, but given the scope, a movement toward native species and more eco-friendly lawns could be very impactful. I also wonder if the current COVID situation might help accelerate the momentum. Many people who are spending more time at home because of the crisis and who are worried about some of the shortages at grocery stores have taken up gardening. I’ve seen several news stories about these so-called “coronavirus victory gardens” (mimicking the victory gardens of the WWII era) that have become very popular. While this kind of gardening might not help with water conservation, I imagine it could have a positive impact on wildlife such as bees and or decrease heat islands in urban areas.

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  6. thank you @Frankschippers98 for your reply. While I am not certain of the numbers I do believe vegetation actually decreases the amount of evapotranspiration from soils. Meaning rather less than more humidity during the initial heatwave. Over long periods of drought the initial evaporation would be diminished but the water will, of course, evaporate over a longer period of time causing more humidity later during the drought.

    Your solution of subsidizing makes sense. I believe this would be more beneficial, I do wonder from what resource these subsidies must come, but this is something that municipalities may be able to fiugre out. Setting contractual regulations would also be a good solution, but will in the end come down to the same result: people who have too little green in their garden will have to pay for this (though being fined for breaking contract and paying taxes are of course essentially different things)

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  7. @mbiles thank you for your addition. Its great to see people more involved with gardening and definitely improving biodiversity and decreasing UHI’s. Even water management is improved greatly through gardening (just the difference between a tiled floor and a bed of flowers is immense)

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  8. @jaspstevens I believe a combined subsidy and tax system would work wonders, thats a great idea. Reward the people doing well using the revenue from the people paying for the right to not improve their gardens.

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  9. @meganrossouw While i believe there would be great opportunity to extend this to green roofs we have to keep in mind that transforming a roof to a green roof could be rather expensive. And people may start building roofs that cannot become green roofs, just in order to evade being forced into making their roof green. For green roofs subsidizing would be the best possiblity i believe, without taxing people that refrain from making their roof green

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