This Permaculture Research Institute article has some interesting videos about projects to attract more backyard wildlife. I don’t think I could convince my urban neighbors that these are a good idea (a “hotel” for centipedes and bees?) They need some adaptation and scaling for urban areas. It could be done though. I especially like the idea of girls playing with bugs – it is natural for children to be covered in bugs most of the time and modern society has gotten away from that.
Tag Archives: urban ecology
urban bee habitat
The BBC has an article on urban habitat for bees:
There is widespread concern that wild bee populations in rural areas are being adversely affected by a number of factors, including pesticides.
“For a bee species to be present in [an urban] habitat, it must be able to find food and nesting substrate,” said co-author Laura Fortel, a researcher from the French National Institute for Agricultural Research (INRA).
“Urban and periurban (the transition between rural and urban) sites can provide high quantities of flowers all year long; they show a high diversity of land cover types and are often warmer than surrounding landscapes.”
She added: “Also, such habitats are seldom treated with pesticides, which are involved in the decline of bees elsewhere.”
It seems like a reversal of conventional wisdom that cities could be important reservoirs of biodiversity when rural agricultural areas have become degraded. In a way it is a negative story, but in another way it is reminder that we should not cynically assume that urban landscapes are always biological dead zones. There is a lot we can do to make them much more ecologically functional for important species of pollinators and birds. If it is happening to some extent by accident, then it could work even better if we did it by design. We can think about how the individual small patches are designed, then think about how they can connect better to each other, to larger urban parks, and to the rural landscape.
Subirdia
Welcome to Subirdia: Sharing Our Neighborhoods with Wrens, Robins, Woodpeckers, and Other Wildlife
NPR reviews an upcoming book called Subirdia, which says that in temperate areas, there are more bird species in the suburbs than in cities or even forests:
So what have suburbs got that forests don’t? Suburbs, he says, offer a wide range of artificially designed garden habitats, providing a smorgasbord of nuts, fruits, seeds, insects and ponds, in dense concentrations. Because they are rich with different kinds of bird food, suburbs are rich with different kinds of birds…
But let’s not get crazy about this: suburbs are not the birdiest zones on earth. Any patch of tropical forest, with its dazzling populations of plant and animal life, will trump a garden-rich suburb. But if you are comparing suburban bird diversity to temperate wild spaces — say the Cascades, the Smokies or the Adirondacks — the suburbs, shockingly, win.
So maybe our goal in denser cities should be to create a landscape with more of this variety of garden habitats. That is doable, and a much more attainable goal than trying to create forest-like habitat in cities. There are some shy species that won’t come to the city, but the city can be pleasant for a wide variety of species, even humans, if we work at it.
nurse trees
I find the idea of “nurse trees” interesting. From Wikipedia:
A nurse tree is a larger, faster-growing tree that shelters a smaller, slower-growing tree or plant. The nurse tree can provide shade, shelter from wind, or protection from animals who would feed on the smaller plant.
Eventually the younger plant outcompetes the older one, and the older one dies, or I suppose it can be cut down by humans. I am thinking about how to apply these ecological concepts to give a helping hand in more urban areas. In my professional work on stormwater management, we often dig up urban soils and replace them with a manufactured soil mix that is more permeable to water and better for plant growth. But all that digging and trucking and waste disposal has a cost and an environmental impact, when we are doing all this to try to help downstream water quality. Maybe we can use carefully chosen trees or plants early on to loosen and add organic matter to the urban soils, then come back a year or two later and plant the trees and plants that we want for the long term. Even better if there is some plant mix where the first phase is faster growing, but then gradually gets out-competed by the second phase, just like the nurse tree concept described above.
green roofs
Green roofs are still pretty expensive and not all that common, at least in North America. But here’s a study in Ecological Engineering where they turned out to work better than people thought in Hong Kong, a humid subtropical area.
Urbanization replaces permeable surfaces with relatively impervious ones to intensify mass and temporal response of stormwater runoff. Under heavy rainfalls, urban runoff could impose tremendous stress on the drainage systems, contributing to combined sewer overflow and flooding. Green roof offers an on-site source-reduction sustainable stormwater management measure that mimics pre-development hydrologic functions. It can retain and detain stormwater as well as delay and suppress peak discharge. However, previous studies were conducted mainly outside the tropics. Since green-roof hydrologic performance can be notably influenced by local meteorological conditions, dedicated investigation in the tropics are necessary. Moreover, substrate depth has long been regarded as an influential factor in green-roof stormwater retention, but recent findings have implicated that such relationship may be more complex. This study (1) evaluates green roof stormwater mitigation performance and potentials in humid-subtropical Hong Kong; and (2) investigates systematically the effect of substrate depth and addition of rockwool, a high water-retention growth medium, on quantitative performance. Using multiple 1.1-m2 raised green-roof platforms placed on an urban rooftop, the effect of four substrate-depth treatments on stormwater mitigation performance was examined over a 10-month study period. The results show that, while the retention under Hong Kong’s frequent and heavy rainfall regime seems to be less effective, remarkable peak reduction and peak delay were evidently expressed even when the green-roof systems have reached full moisture-storage capacity. No statistical significance was found between treatments, despite the slightly higher mean performance of the 80-mm soil substrate. Satisfactory peak performance of the 40-mm soil substrate implies that a thin substrate can provide effective peak mitigation, especially if building loads are of concern. Extensive green roof remains as a promising alternative mitigation strategy to urban stormwater management in Hong Kong with potential application to other tropical areas.
Part of me doesn’t like using an inorganic material like rockwool. But if somebody comes up with a simple, cheap material that we can practically just staple or spray on to roofs in urban areas, it could be a quick way to restore a lot of hydrologic function – retention, evaporation, peak flow reduction, and cooling – in urban areas. It could be a transitional step on our way to restoring both hydrologic and ecological functions together – ideally we would want to capture that water and use it to grow something of use to either people or wildlife or both. But we are far from ideal today, so I’m all for some smaller steps in the right direction.
functional urban streams
If you want a functional urban aquatic ecosystem, you don’t get it just through half-hearted management measures in the area draining to the stream. You have to get in there and make a functional ecosystem, and then you might be able to protect and sustain it by managing the watershed better. The article in Restoration Ecology looks at a range of numbers from the literature that make the case pretty well:
Urban development is a leading cause of stream impairment that reduces biodiversity and negatively affects ecosystem processes and habitat. Out-of-stream restoration practices, such as stormwater ponds, created wetlands, and restored riparian vegetation, are increasingly implemented as management strategies to mitigate impacts. However, uncertainty exists regarding how effectively they improve downstream ecosystems because monitoring is uncommon and results are typically reported on a case-by-case basis. We conducted a meta-analysis of literature and used response ratios to quantify how downstream ecosystems change in response to watershed development and to out-of-stream restoration. Biodiversity in unrestored urban streams was 47% less than that in reference streams, and ecological communities, habitat, and rates of nutrient cycling were negatively affected as well. Mean measures of ecosystem attributes in restored streams were significantly greater than, and 156% of, those in unrestored urban streams. Measures of biodiversity in restored streams were 132% of those in unrestored urban streams, and indices of biotic condition, community structure, and nutrient cycling significantly improved. However, ecosystem attributes and biodiversity at restored sites were significantly less than, and only 60% and 45% of, those in reference streams, respectively. Out-of-stream management practices improved ecological conditions in urban streams but still failed to restore reference stream conditions. Despite statistically significant improvements, assessing restoration success remains difficult due to few comparisons to reference sites or to clearly defined targets. These findings can inform future monitoring, management, and development strategies and highlight the need for preventative actions in a watershed context.
So let’s focus more on function and worry less about structure in our urban ecosystems. Let’s not settle for making them less bad. Let’s make them good!
restoring the American Chestnut
I like this abstract in Restoration Ecology on the most efficient way to reseed the American Chestnut to eastern forests.
Efforts are underway to return the American chestnut (Castanea dentata) to eastern forests of North America following its decline due to the introduction of the chestnut blight (Cryphonectria parasitica). Approaches include developing blight-resistant chestnut lines through breeding programs and via genetic engineering. Reestablishment of resistant chestnut to eastern forests would produce one of the most extensive ecological restoration transformations ever attempted. However, this undertaking is costly and optimization of reintroduction methods is needed. We used the computer program NEWGARDEN to model whether some patterns of founder placement (regular vs. random spacing at differing densities) produce more rapidly expanding populations across a range of gene dispersal distance conditions (via both offspring and pollen). For a simulated introduction project employing 169 founders, placing founders randomly in a square of side 0.85 km produced higher rates of predicted population growth compared with larger or smaller squares under near gene dispersal conditions; this side distance was 1.0 km under far gene dispersal conditions. After 100 population bouts of mating and under near gene dispersal conditions, the trial with founder placement producing the greatest population expansion rate exhibited a 314% increase in census size compared with the founder pattern yielding the slowest expansion. Neither loss of alleles nor inbreeding or subdivision was significantly increased under the founder placement patterns yielding the most descendants. Exploring different numerical and geometrical founding scenarios using NEWGARDEN can provide first estimates of founding patterns or stand manipulations that will return the most descendants produced per founder planted in restoration projects.
So it is possible to give an ecosystem a helping hand. Maybe we can use similar principles not just to restore species and ecosystems that used to exist, but to create truly functional ecosystems in rural, suburban, and urban areas and the transitions between them.
the future of urban transportation
I like the vision of future urban transportation laid out in this article from Atlantic CityLab:
My utopian vision of how this could play out is to rededicate a lot of space in cities that was de facto applied to cars in the 1950s, after the death of the streetcars and the explosion of expressways, over to active transportation. Cars entering city limits would have to be autonomous or switched to driverless mode, as these will be deemed safe for all users of the transportation system and will operate in much less road space than drivers need now. (As a reference point, auto accidents are the leading killer of young people worldwide.) Parking needs could decrease dramatically, too, as most autonomous vehicles will be on-demand and active, compared to the 95 percent of time that current cars sit parked. We would have a transit backbone consisting of heavy and light rail/streetcars, and regional/arterial buses. The rest of the network and space would be slanted towards walking, bike-share, and other alternative modes.
I don’t necessarily think this is a “utopian vision”. I think a lot of it is just going to happen and is already happening. Enormous amounts of space that have been devoted to car maneuvering and parking are going to be available for other uses. The question is, are we just going to let all the space sit there or have a good plan for what to do with it? Some of it can be used for housing and economic activity, some for parks, wildlife habitat and movement corridors, and food growing, and some for managing water or harvesting solar energy. And of course, combinations of these are possible. But we do need to have a vision and a plan, which some can call “utopian” if they so choose.
falling fruit
This website, called Falling Fruit: Mapping the urban harvest, is attempting to be a worldwide map of harvestable food in urban areas. I think this is a great idea both for sustainability and for livability in urban areas. There must be a lot of fruit and nut trees on private land and in forgotten spaces of public land – median strips, the “tree lawn” between street and sidewalk, and so forth. But in many cases the people who own or control this land may not be interested in taking care of these trees. At the same time, I believe there are a lot of frustrated urban armchair gardeners out there who would love to take care of them, but don’t have permission to access the private property, or don’t know about or feel comfortable taking care of the trees on the public property. So a website like this could begin to connect the trees to the people who are willing to take care of the trees.
That’s just the trees we have now. If something like this took off, we could gradually replace more of our ornamental urban landscaping with edible landscaping – fruit hedges, strawberry lawns, and so on. We could incorporate rain barrels, rain gardens, compost bins, even chickens and rabbits for people who are open to that. We could take wildlife habitat into account to, and start to take a larger view of the landscape – how patches of urban habitat can be connected, and how patches of urban habitat can be connected to larger urban parks and rural reserves.
By the way, I don’t mean for urbanism to be the primary subject of this blog. The subject is how our civilization is connected to, and impacting, and dependent on, the natural world and what that means for the future. But at the risk of stating the obvious, urban areas are where the people are so I will return to urban design and urban hydrology and urban ecology and land use and transportation topics fairly often.