Showing posts with label Urban. Show all posts
Showing posts with label Urban. Show all posts

Monday, December 21, 2020

Bright Goes North

Guest post by Kate Davies, a recent MEnvSc Graduate from the University of Toronto-Scarborough


She could feel the pull in her body. It was time.

She had done this journey before, but even the first time it felt familiar. Like a memory that she was born with.

She was called Bright because she was known by the others for her deeply golden tail feathers and her clear eyes. Bright was late leaving her winter home this year, and many of the others had left already, departing at the first signs of change. The air had started to feel heavy signaling that the rains would come soon. She had to start north before daybreak. Bright hopped around the tree canopy from branch to branch. She dropped her wings by her sides and fanned her tail to spook the insects and quickly grab them in her beak. She had spent her winter in brushy scrubland that was not the best feeding grounds, but she was older now and had less energy to defend her place in the boggy wetlands filled with ripe insects. She ate her fill before she spread her wings and started to carry her small light body out over the immense open waters. Crossing the gulf was frightening the first time, but she knew even on her first trip that the sky would end, and she would see green again. She traveled in a loose flock with some other Redstart females, some yearlings and others Bright knew from previous flights. She hoped some of her daughters were here, now grown she would not have known their calls. The males always left first; they would meet them in the northern home.

Illustration by Kate Davies

The journey across the gulf lasted into the night, the winds were not favourable this year. Bright and the others she travelled with were weak and needed to eat. There was a wetland they had visited as a stop every year, but Bright was worried they had taken a wrong turn. This was the right place but there was not water, few plants, and it had been filled with stone, humans and a glowing hum. It seemed as she flew north every year there were more angular stone forests filled with humans. Some could tolerate these stone forests but Bright and her companions preferred trees and grass. The birds who lived there like pigeons and house sparrows spoke a different language than the other birds she knew, and some said they came across the water bigger than the gulf. So, despite their exhaustion the females kept flying until they could find somewhere to eat and sleep. They had to settle for an area where the plants all grew in rows, a farm, but there was a river and some insects so it would do for today. These human places had different dangers and predators than in the forests and fields. Bright knew to be cautious of owls, hawks and snakes but where there were humans, other dangers were lurking. They were too tired to find anywhere else to sleep. Bright noticed that her party had shrunk by a few - some were so tired they may have rested in the stone forest. Bright hoped the others would be alright and would catch up to the group.

They travelled for a few more days, finding quiet places to rest. They avoided the stone forests as much as they could with their bright lights, constant noises and hums. They rested at another farm on the fifth night. Bright and her companions were huddled in a dense thicket of bushes near a field and river. They had fallen sound asleep for the night. In the nearby tall grasses, a pair of green eyes shone in the moonlight. A barn cat had been stalking the birds, she moved quietly, softer than the wind. The cat slinked under the low branches of the bush without a sound and spotted a bird on a low branch she could easily reach.  Bright opened her eyes to see one of the yearlings was in the cat’s fangs - she was lost. Bright and her companions moved to another row of bushes closer to the stream, they were all shaken and tired. Fear and anxiety overtook the small flock, they didn’t sleep anymore that night. Bright was relieved when the sun crept over the horizon and they could continue northward.

Illustration by Kate Davies

The air was warm, and they had been lucky that there were no storms along the way. They started to see some males that day, and a few of her companions ended their journey to find a mate. Bright continued her northward flight as did most of the females until they made it over the big lake. It was not as big as the gulf, but it could be dangerous, as there were many humans and stone forests around the water. There were predators near every shore, some had been here all winter and were eager for the small songbirds to return so they could fill their bellies.

Since Bright had left late this year, she was eager to build a nest and find a mate. She decided to end her journey on an island at the north shore of one of the long lakes. Most of the others continued north. She was near a stone forest but on an island that was far enough away that the sound of the waves drowned out the hum and noise. It was the time of year where the air was filled with song from many different birds. She fluttered around the island listening for males of her kind, trying to find one who sang strong and clear. She followed a song to a male high up in a red maple tree. In her mind she identified him as Flicker - he was very expressive in the way he flicked his tail. He took her to the sites he had scouted for nesting to see if she approved of any. She was happy that she would be his first and maybe only mate, which would afford her more protection. She picked the third site he showed her. It was a dense area of red dogwood that was covered in fresh young leaves. They were close to a pond in an area rich with insects. She started to gather twigs and build her nest there while Flicker stayed close singing to warn others away from his mate and territory. Together they had four eggs and Bright was happy with her clutch size; it was more than last spring. She left the nest to find some food in early morning and Flicker guarded the eggs. She was chasing a particularly acrobatic fly though the bushes when suddenly a great force stopped her flight and she fell to the ground. She could feel and taste the warmth of blood in her mouth, her beak was fractured, her head pounded, and she could not catch her breath. She had only seen branches before her, it was like a reflective pond in the air made of stone. Bright wanted to live, she wanted to get up go back to Flicker and the young. She could not move; she let out her last breath and died.

The new gardener came around back of the building to trim the forsythia that was long overgrown. At the base of the bush under the window lay a female American Restart, she was dead. The garden gasped and cried out ‘Oh no!’ Another window strike, this was the sixth one this month and perhaps it would encourage management to finally birdproof the windows, thought the gardener. She buried the bird in the garden with a tear for its loss of life and trimmed the forsythia. On her break she reported the window strike on the Fatal Light Awareness Project (Flap) website and continued her duties.

Flicker realized that Bright would not return - what had become of her? He could not care for the babies alone. He would have to leave them. He sung a mournful song for Bright and flew off in search of a new mate hoping that it wasn’t too late.

 

 

Further Reading and References

Further reading: Online resources

The Cornell Lab - All about birds – American Redstart

Overview: https://www.allaboutbirds.org/guide/American_Redstart/overview and

Species account: https://birdsna.org/Species-Account/bna/species/amered/introduction

Toronto and Region Conservation Authority. The American Redstart: A Bird On the Rise In the GTA https://trca.ca/news/the-american-redstart-a-bird-on-the-rise-in-the-gta/

Boreal Songbird initiative. A guide to boreal birds https://www.borealbirds.org/bird/american-redstart

Ontario Nature. Migratory Birds https://ontarionature.org/campaigns/migratory-birds/

North American Birds Declining as Threats Mount By Mel White for National Geographic https://www.nationalgeographic.com/news/2013/6/130621-threats-against-birds-cats-wind-turbines-climate-change-habitat-loss-science-united-states/

Birdwatchers Digest. Your Bird Questions Answered: Flight and Migration https://www.birdwatchersdigest.com/bwdsite/connect/youngbirders/your-bird-questions-answered-flight-migration.php

 

 Further reading: peer reviewed literature

Cohen, E. B., Rushing, C. R., Moore, F. R., & Hallworth, M. T. (2019). The strength of migratory connectivity for birds en route to breeding through the Gulf of Mexico. Ecography, 42(4), 658–669. https://doi.org/10.1111/ecog.03974

Cooper, N. W., Sherry, T. W., & Marra, P. P. (2015). Experimental reduction of winter food decreases body condition and delays migration in a long-distance migratory bird. Ecology, 96(7), 1933.

Hill, G. E. (2004). A Head Start for Some Redstarts. Science, 306(5705), 2201–2202.

Germain, R. R., Marra, P. P., Kyser, T. K., & Ratcliffe, L. M. (2010). Adult-Like Plumage Coloration Predicts Winter Territory Quality and Timing of Arrival on the Breeding Grounds of Yearling Male American Redstarts. The Condor, 112(4), 676–682. https://doi.org/10.1525/cond.2010.090193

Norris, D. R., Marra, P. P., Bowen, G. J., & Ratcliffe, L. M. (2006). Migratory connectivity of a widely distributed songbird, the American Redstart (Setophaga ruticilla). The Auk, 123(4), 14.

Norris, D. R., & Marra, P. P. (2007). Seasonal Interactions, Habitat Quality, and Population Dynamics in Migratory Birds. The Condor, 109(3), 535–547.

Marra, P. P., & Holmes, R. T. (2001). Consequences of Dominance-Mediated habitat segregation in American Redstarts during the nonbreeding season. The Auk, 118(1), 92–104.

McKinnon, E. A., Stanley, C. Q., & Stutchbury, B. J. M. (2015). Carry-Over Effects of Nonbreeding Habitat on Start-to-Finish Spring Migration Performance of a Songbird. PloS One, 10(11), e0141580.

Morris, S. R., & Glasgow, J. L. (2001). Comparison of spring and fall migration of American Redstarts on Appledore Island, Maine. The Wilson Bulletin, 113(2), 202.

Smith, R. J., Mabey, S. E., & Moore, F. R. (2009). Spring Passage and Arrival Patterns of American Redstarts in Michigan’s Eastern Upper Peninsula. The Wilson Journal of Ornithology, 121(2), 290–297. https://doi.org/10.1676/08-051.1

Wuethrich, B. (1998). Songbirds Stressed in Winter Grounds. Science, 282(5395), 1791–1794.

 

 


Monday, March 30, 2020

Early evidence that governmental responses to COVID-19 reduce urban air pollution

There is no doubt that the global spread of COVID-19 represents the defining crisis of the last decade. Governments around the world have scrambled to try to reduce person-to-person spread and deal with pressures on public health infrastructure. Regions with community spread have almost universally faced restrictions on travel, business and social activities. These restrictions are designed to reduce the exponential spread of COVID-19 (that is, to flatten the curve), these restrictions will also have a large number of other economic, social and environmental repercussions. Here, I ask a simple question: Has reductions in economic activity and movement caused by governmental responses to COVID-19 improved air quality in cities? I compare February 2019 and 2020 air quality measures and show that six cities that were impacted early by government restrictions in response to COVID-19 show consistent declines in five of six major air pollutants compared to cities that were impacted later (the text in this post has been modified from Cadotte 2020).


One of the most pernicious and inevitable consequences of urbanization and industrialization is the release of air pollutants. The WorldHealth Organization (WHO) estimates that about 90% of urban residents experience air pollution that exceeds WHO guidelines and that air pollution is responsible for more than four million premature deaths annually (World Health Organization 2018). Air quality is adversely affected by the aerosol release of a number of chemical compounds from agriculture, manufacturing, combustion engines and garbage incineration, and is usually assessed by measuring the atmospheric concentrations of six key pollutants: fine particulate matter (PM2.5), course particulate matter (PM10), ground-level ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO). These pollutants have a number of serious human health impacts (Table 1). Reducing inputs of these pollutants into urban areas requires a combination of technological advancement and behaviour change that can be stimulated by governmental regulations and incentives.


Table 1: The six commonly measured air pollutants in cities and their human health impacts.

Alterations of human, transport and industrial activity are usually the result of long-term economic and behavioural change and difficult to legislate under normal situations. However, the recent emergence of the global COVID-19 pandemic has had clear epidemiological impacts with, as of March 25, 2020, almost half a million confirmed infections and close to 20,000 deaths (World Health Organization 2020). This pandemic has resulted in emergency measures attempting to reduce transmission rates that limit activity, movement and commerce in jurisdictions around the world. While these emergency measures are critically important to limit the spread and impact of the coronavirus, they also provide a glimpse into how governmental calls for behavioural change can alter air pollution levels in cities.

Early evidence reveals that pollution levels have dropped in places that have undergone COVID-19 shutdowns. As Marshall Burke showed in a blog post,  PM2.5 and PM10, levels are lower than expected in parts of China. Here I examine January and February 2020 AQI levels for the six pollutants in Wuhan to what would be expected under normal circumstances. I further compare the change in February air pollution levels over the past two years in six cities that instituted emergency measures by the end of February (early impacted cities) to 11 cities that did not declare states of emergency until March (later impacted cities) using freely available air monitoring data (World Air Quality Index Project 2020) -see Table 2 for a list of cities.

Table 2: The eleven cities used in this analysis, the month that emergency measures were enacted and two- to six-year AQI averages of the pollutants
City-data come from monitoring agencies listed at the end of this post

Wuhan, China was the epicenter for the December 2019 emergence and the first person-to-person spread of the novel coronavirus.  In response, authorities initiated a series drastic measures limiting human movement and activity in Wuhan and large parts of Hubei province by the end of January. Three air pollutants: PM2.5, PM10 and NO2 all showed substantial January and February declines in Air Quality Index (AQI) (U.S.Environmental Protection Agency 2014) values over 2019 levels for those months and what would be expected from long-term trends (Fig. 1). These long-term declining air pollution trends do reveal that China’s recentpollution reduction and mitigation efforts are steadily paying off, but the government-enforced restrictions further reduced pollution levels. The expected air pollution values predicted by temporal trends (red dashed lines in Fig. 1) are all substantially higher than the observed levels, with observed values being between 13.85% lower than expected for January PM2.5 and 33.93% lower for January NO2. Further, the reductions in the pollutants shown in Fig. 1 increased the number of days where pollutant concentrations were categorized as ‘good’ (0 < AQI < 50) or ‘moderate’ (51 < AQI < 100) according to the AQI. The three other pollutants: SO2, O3 and CO, all showed idiosyncratic or non-significant changes, mostly because their levels have already reduced significantly over time or appear quite variable (Fig. 2). 

Fig. 1. Temporal patterns of Air Quality Index (AQI) PM2.5, PM10 and NO2 values in Wuhan, China. Both January and February, 2020 values show significant declines compared to 2019 levels and to that predicted from long-term trends (red dashed line).

Fig. 2. Temporal patterns of Air Quality Index (AQI) SO2, O3 and CO values in Wuhan, China.

Once COVID-19 moved to other jurisdictions, and confirmations of community spread emerged in February 2020, emergency measures, like those in Hubei province, were instituted to limit human movement and interaction. The cities subjected to February restrictions include, in addition to Wuhan, Hong Kong, Kyoto, Milan, Seoul and Shanghai, and the AQI values from these cities were compared to other cities that did not see the impacts of the novel coronavirus or have emergency restrictions in place until well into March. Log-response ratios between the air concentrations of pollutants observed in February 2020 to those from February 2019 reveal that all air pollutants except O3 show a decline in the 2020 values for the early impacted cities (Fig. 3). For later impacted cities, there is no overall trend in changes in the concentrations of pollutants between 2020 and 2019 and the individual cities in this group showed less consistency in the differences between years (Fig. 3). 

Fig. 3. Log response ratios for Air Quality Index (AQI) PM2.5, PM10, NO2, O3, SO2 and CO values between February 2019 and February 2020 values. Negative values indicate a decline in 2020. The green symbols indicate values from an assortment of cities that did not have emergency measures in place until March, 2020 (later impacted cities) and orange symbols are for cities that were impacted by the end of February.
These results indicate consistent air pollution reduction in cities impacted early by the spread of the novel coronavirus. However, the analyses presented here require further investigation as governments increasingly restrict activity world-wide, and some are discussing the possibility of prematurely lifting restrictions in order to spur economic growth. Further, the data analyzed here present point estimates of air quality but air pollution impacts are not homogeneous through urban landscapes and is influenced by spatial variation in industrial activities and transportation (Adams & Kanaroglou 2016). Thus, as higher resolution spatial air pollution data become available, it would be valuable to see how reduced activity affects air quality in different parts of cities.

This analysis of early data indicates that governmental policies that directly reduce human activity, commercial demand and transportation can effectively and quickly reduce urban air pollution. While the COVID-19 pandemic represents a serious risk for health and wellbeing of populations globally, especially those living in high density urban areas, the impacts of air pollution are equally consequential. If governments are willing to expend trillions of dollars in direct funding and indirect economic costs to combat this disease, then why do these same governments permit or even subsidize activities that emit air pollution? Maybe the lessons learned with COVID-19 can serve as the impetus for further action. Perhaps mandating changes to economic or transportation activity or investing in clean technology would better protect human health from the effects of air pollution.

Cited sources
Adams, M.D. & Kanaroglou, P.S. (2016) Mapping real-time air pollution health risk for environmental management: Combining mobile and stationary air pollution monitoring with neural network models. Journal of environmental management, 168, 133-141.
Cadotte, M. W. (2020) Early evidence that COVID-19 government policies reduce urban air pollution. Retrieved from eartharxiv.org/nhgj3
Cesaroni, G., Forastiere, F., Stafoggia, M., Andersen, Z.J., Badaloni, C., Beelen, R., Caracciolo, B., de Faire, U., Erbel, R. & Eriksen, K.T. (2014) Long term exposure to ambient air pollution and incidence of acute coronary events: prospective cohort study and meta-analysis in 11 European cohorts from the ESCAPE Project. Bmj, 348, f7412.
Fann, N., Lamson, A.D., Anenberg, S.C., Wesson, K., Risley, D. &Hubbell, B.J. (2012) Estimating the National Public Health Burden Associated with Exposure to Ambient PM2.5 and Ozone. Risk Analysis, 32, 81-95.
Greenberg, N., Carel, R.S., Derazne, E., Bibi, H., Shpriz, M., Tzur, D. & Portnov, B.A. (2016) Different effects of long-term exposures to SO2 and NO2 air pollutants on asthma severity in young adults. Journal of Toxicology and Environmental Health, Part A, 79, 342-351.
Kampa, M., & E. Castanas. (2008) Human health effects of air pollution. Environmental Pollution, 151, 362-367.
Khaniabadi, Y.O., Goudarzi, G., Daryanoosh, S.M., Borgini, A., Tittarelli, A. & De Marco, A. (2017) Exposure to PM 10, NO 2, and O 3 and impacts on human health. Environmental science and pollution research, 24, 2781-2789.
Raaschou-Nielsen, O., Andersen, Z.J., Beelen, R., Samoli, E., Stafoggia, M., Weinmayr, G., Hoffmann, B., Fischer, P., Nieuwenhuijsen, M.J. & Brunekreef, B. (2013) Air pollution and lung cancer incidence in 17 European cohorts: prospective analyses from the European Study of Cohorts for Air Pollution Effects (ESCAPE). The lancet oncology, 14, 813-822.
U.S. Environmental Protection Agency (2014) AQI: Air Quality Index. Office of Air Quality Planning and Standards, Research Triangle Park, NC.
World Air Quality Index Project (2020) https://waqi.info/.
World Health Organization (2018) Ambient (outdoor) air pollution: https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health.
World Health Organization (2020) Coronavirus disease 2019 (COVID-19), Situation Report –65.

City air quality monitoring agencies:
1 Division of Air Quality Data, Air Quality and Noise Management Bureau, Pollution Control Department, Thailand (http://aqmthai.com).
2 Delhi Pollution Control Committee (http://www.dpccairdata.com).
3 Hong Kong Environmental Protection Department (http://www.epd.gov.hk).
4BMKG | Badan Meteorologi, Klimatologi dan Geofisika (http://www.bmkg.go.id).
5South African Air Quality Information System - SAAQIS (http://saaqis.environment.gov.za).
6 Japan Atmospheric Environmental Regional Observation System (http://soramame.taiki.go.jp/).
7 UK-AIR, air quality information resource - Defra, UK (http://uk-air.defra.gov.uk).
8 South Coast Air Quality Management District (AQMD) (http://www.aqmd.gov/).
9 INECC - Instituto Nacional de Ecología y Cambio Climático (http://sinaica.inecc.gob.mx).
10 Agenzia Regionale per la Protezione dell'Ambiente della Lombardia (http://ita.arpalombardia.it).
11 CETESB - Companhia Ambiental do Estado de São Paulo (http://cetesb.sp.gov.br).
12 Department of Public Health of the Sarajevo Canton (http://mpz.ks.gov.ba/).
13 Air Korea Environment Corporation (http://www.airkorea.or.kr).
14 Shanghai Environment Monitoring Center (http://sthj.sh.gov.cn).
15 Israel Ministry of Environmental Protection (http://www.svivaaqm.net).
16 Air Quality Ontario - the Ontario Ministry of the Environment and Climate Change (http://www.airqualityontario.com/).
17 Wuhan Environmental Protection Bureau (http://www.whepb.gov.cn/).

Thursday, March 12, 2020

The Homogenization of Urban Macro-systems

*This post is by Rabia Ahmed, a student in Marc's 'Causes and Consequences of Diversity' class.


If you have ever walked along a residential street in the city or suburbs you will notice many similar features in each backyard. Often times personal gardens are representative of peoples’ identities and reflect their membership in the neighbourhood. With the expansion of the urban population, an increasing area is covered by personal yards. While each homeowner views their yard to be small and therefore quite insignificant to the overall ecosystem- aggregated across the country, this area quickly adds up. 


 Despite the expansion of urban ecosystems little research has been devoted to understanding the patterns of ecosystem biodiversity, function and assembly. The findings of a recent paper by Pearse et al. (2018) investigated the extent to which “residential macro-systems” are the same across different US cities. The main focus of the paper was to compare the diversity, composition and structure of cultivated yards to the natural ecosystem in different climates across the US.

The results of the study showed that indeed the phylogenetic and species composition in yards had greater homogenization across regions compared to the corresponding natural ecosystems. There was also evidence of homogenization in vegetation as the tree density in yards remained similar across regions, despite the fact that, due to environmental filters, the tree densities in the different urban climates varied significantly. For example, the natural ecosystems in Salt Lake City and Los Angeles almost had no trees, but the tree density in the yards was well above zero.



Figure 1. The above diagram shows the convex hulls (dashed line) for three species pools: cultivated (orange), spontaneous (blue) and natural (green). The regions are abbreviated, Boston, Baltimore, Los Angeles, Miami, Minneapolis–St. Paul, Phoenix, and Salt Lake City as BOS, BA, LA, MI, MSP, PHX, and SL, respectively. The data shows that cultivated and spontaneous pools are more similar across regions than natural area pools, and in all cases, pools in the same geographical area are more similar than pools across a geographical region.
(Retrieved from Pearse et al. 2018)

Surprisingly, however, it was found that urban vegetation whether directly planted or spontaneously growing in the yards, had greater species richness than the comparative natural areas. The greatest phylogenetic diversity (MPD) was found within the fully cultivated yards, suggesting that these species would be better suited to future climate stressors due to their evolutionary distinctiveness. This variation in species lineages provides evidence that people prefer to have a variety of plants and flowers in their backyards which are not often found in the species pool.

Overall the data suggests that similarities in land cover and residential structural characteristics lead to a decrease in microclimate divergence at a continental scale.
These results underscore the common human preference for maintaining yards that are aesthetically pleasing and low maintenance. This homogenization has broad implications as it takes effort to keep these ecosystems the same, across forests, deserts and planes. For example, it has been observed that there is little difference between the amount of irrigation and fertilizers used by homeowners in the driest (Phoenix) or the wettest (Miami) cities.

While many argue that urban and suburban habitats do not compare to natural landscapes, recent research shows that they are more biologically diverse than previously assumed. The increased biodiversity is mostly because of the fact that people plant non-native species along with the native species, and artificial maintenance is used to overcome the environmental filter. Therefore, artificially enriched environments such as yards have both positive and negative consequences on the surrounding environment. For instance, researchers at Boston University found that trees in urban yards grow twice as fast as those in nearby forests, and store carbon at a faster rate. On the other hand, it was found that the rich mulched soils in suburban yards emitted twice as much CO2 as the soil in rural forests.

In conclusion, although yards have been given diminished importance in the study of human-dominated environments, they can provide great insight into how we can make our communities more sustainable. Residents, municipalities and neighbourhood associations can help reshape their residential macro-system into a thriving eco-system one backyard at a time. The key is to keep a balance between human preferences and other organisms’ needs, thus designing landscapes that are not only aesthetically pleasing but also support pollinators and birds.



References

Groffman, Peter M., et al. “Satisfaction, water and fertilizer use in the American residential macrosystem.” Environment Research Letters, vol.11, 29 Feb. 2016, doi:10.1088/1748-9326/11/3/034004
Humphries, Courtney. “The Residential Macrosystem.” Anthropocene, 21 June 2017, www.anthropocenemagazine.org/2017/06/residential-macrosystem-backyard-science/.
Pearse, William D., et al. “Homogenization of Plant Diversity, Composition, and Structure in North American Urban Yards.” Ecosphere, vol. 9, no. 2, 15 Feb. 2018, doi:10.1002/ecs2.2105.





Wednesday, September 7, 2016

Where the wild things are: the importance of urban nature

Cities represent our ultimate domination over nature. They are landscapes that are completely modified to meet all of our needs and desires. In cities we drastically change the vegetation, reroute rivers, seal the Earth’s surface in impermeable cement, and often change the chemical composition of the air around us. For most people, this unnatural state of affairs seems completely natural. Its how we grow up.

What we don’t notice is all that is missing. The trees, the birds, and the mammals are largely absent from big cities. But not all cities are equal in this missingness. For those of us that live in cities like Toronto, Nashville, or Sydney, seeing birds and mammals is part of our normal life. In my back yard in Toronto, I am likely to see racoons, skunks, possums, red squirrels, eastern grey squirrels, chipmunks, deer mice, and a plethora of birds, and just down the road, foxes, coyotes, and deer are not uncommon. One morning I heard a ‘thud’ come from our sunroom window, and outside was a stunned red-tailed hawk (he was fine in the end). These cities are evidence that nature can persist and coexist with urban development.

However, there are other cities where nature is almost completely absent. While living in Guangzhou, China I saw just cats, dogs and rats, and barely any birds –shockingly no pigeons. Recently in while in Montpellier, France, it became obvious to Caroline and I (the two EEB & Flow contributors) that besides a small lizard species, pigeons and a few sparrows, we were not going to see any wildlife in the city. Guangzhou and Montpellier are very different cities in terms of size (16 million vs. 300 thousand), density, building height, pollution levels, etc.  But one way they are similar is that they are old. People have living and changing the landscapes in these regions for thousands of years. Of course the same could technically be said of North America and Australia, but the magnitude and intensity of human modification has no parallel in North America and Australia. Long-term intensive human activity removes other species in the long run. Is this the natural endpoint for our younger cities?

Cambridge, England. While quite beautiful, it is a typical old european city with a lot of stone.

Why we should celebrate raccoons

Toronto has a war against the raccoon. To most Torontonians, the raccoon is a plague –vermin that get into garbage cans and pull shingles off of roofs. Their density in Toronto is about 10 times higher than in wild habitats and many people in Toronto support removing them all together.

I have a different stance. We should be celebrating the raccoon. Yes raccoons cause problems; yes they carry disease; yes they damage property; yes their density is unnaturally high. But the same can be said of people (I don’t think I ever caught a flu from a raccoon). If raccoons were to recede to distant wilds and disappear from Toronto altogether, we would be no different than all those other cities where nature has completely lost. Raccoons give hope –hope that nature can flourish under the repressive and cruel dominion of urban centres. Raccoons remind us that nature has a place and can thrive in cities, and that we can share this world. They give me hope that Toronto’s destiny is not prescribed and we are not bound to the same fate as so many other cities.

I have a couple of new Chinese scientists visit my lab each year, and the differences between Toronto and say Beijing or Shanghai could not be more stark for them. To see deer, squirrels and raccoons in the city is a marvel. Every time one of these visitors comments on the wildlife in our city, I am reminded that we are really fortunate and have something that should be cherished.

Raccoon family –not an uncommon sight in Toronto (CCBYgaryjwood


Need to rethink urban nature

The problem is that Toronto, and most other cities, is continuing to grow and become more densely packed, making it more difficult for nature to endure. We need to rethink how cities grow and develop, and we need to keep a place for nature. There is no reason why new developments can't accommodate natural elements and green space –this often does not happen in most cities. Singapore is unique in this sense, new public infrastructure projects explicitly incorporate novel green space and infrastructure. I toured green sites there recently and saw a new hospital where it was impossible to tell where the park space ended and the hospital started (see picture below). There I saw patients tending gardens on the roof, nearby residents strolling through the forested courtyards, and turtles, wading birds and a large river monitor in the neighbouring pond. Also, Singapore's new large pump house infrastructure that reduces flooding in the city has a full sloping lawn on the top that is used by picnickers. In most North American cities this type of building would be grey industrial cement with little other function than to house pumps.

Singpore's Khoo Teck Puat hospital -the world's greenest hospital? 

Large old cities devoid of wildlife need not be the natural endpoint for a city.  Smart development and accommodating nature needs to be woven into the tapestry of cities. Toronto’s raccoons are great, and I wouldn’t want to live in a Toronto without them.