The 206th anniversary of Charles Darwin is today, so Happy International Darwin Day!
One big question facing urban wildlife conservation right now is whether or not evolution is happening in front of us. There are certainly behavioral changes that some animals are making in urban areas (some birds sing at a different frequency in cities than their counterparts in rural areas, in order to not have their songs be masked by traffic noise, for example), but the question is whether these changes are being driven by natural selection or by innate plasticity found in the species already (keeping with bird song, maybe they can just sing in different ranges and so choose the appropriate frequency for where they are).
There are also phenotypic changes in some species depending on their surroundings. Perhaps the classic example in urbanized areas are pepper moths in England (although there is some controversy about whether or not this was indeed an example of natural selection, a large, relatively recent study has shown that natural selection alone would account for the change in color in the moths).
My guess is that it’s a bit of both, depending on the species in question and the circumstances of the change. It’s an exciting field of inquiry, and gets to some of the fundamental challenges in conservation biology; if one of our goals is to preserve the possibility of evolution so that species can adjust to changing conditions, then this might be further evidence of the value of urban areas to conservation writ large.
For a good overview of urban wildlife behavior, check out:
Ryan, Amy M., and Partan, Sarah R. 2014. “Urban Wildlife Behavior.” In Urban Wildlife Conservation: Theory and Practice, eds. McCleery, Robert A., Moorman, Christopher E., and Peterson, M. Nils. Pp. 149-174. Springer: New York.
We’ve had a couple of incredibly vivid sunsets in the last few weeks. When I was growing up in Chicago, two of my favorite museums were (and really still are) the Field Museum of Natural History and the Chicago Historical Society. What both have in common are dioramas — for the Field Museum, taxidermied wild animals and the landscapes they belonged in, and for the Chicago Historical Society, Chicago history (of course!). Some of the backgrounds were just stunning — true works of art.
Now, I do have some conflicting feelings about the Field Museum’s dioramas. After all, they do contain dead animals (albeit long-dead animals — some of them from the 1800’s). But there was something magical about them, and very real, and I’m not alone in thinking about their value to education and imagination. In fact, there was just a successful crowdfunding campaign to create a new diorama (using specimens from 1896, but putting them into a new scene); the new hyena diorama was unveiled last month.
In any case, this sunset reminded me of one of those backdrops. Like a painting, but also real.
This week, we celebrated World Wetlands Day, an annual event held on February 2 to mark the anniversary of the adoption of the Convention on Wetlands in 1971 (more commonly known as the Ramsar Convention, after the Iranian city where the meeting took place).
… areas where water covers the soil, or is present either at or near the surface of the soil all year or for varying periods of time during the year, including during the growing season. Water saturation (hydrology) largely determines how the soil develops and the types of plant and animal communities living in and on the soil. Wetlands may support both aquatic and terrestrial species. The prolonged presence of water creates conditions that favor the growth of specially adapted plants (hydrophytes) and promote the development of characteristic wetland (hydric) soils.
Wetlands vary widely because of regional and local differences in soils, topography, climate, hydrology, water chemistry, vegetation and other factors, including human disturbance. Indeed, wetlands are found from the tundra to the tropics and on every continent except Antarctica. Two general categories of wetlands are recognized: coastal or tidal wetlands and inland or non-tidal wetlands.
We do find wetlands in urban areas, of course, in as great of a variety as anywhere else. Wetlands are incredibly important ecosystems for many reasons. They provide essential ecosystem services such as storm water management (a lesson we learned in the aftermath of Hurricane Katrina all too well), water purification, and valuable habitat for many species of both plants and animals.
Urban wetlands often need to function in multiple ways – as habitat, as corridors, as a provider of ecosystem services, and – perhaps controversially at times – as recreational areas for people. Zedler and Leach remarked in the late 1990’s that three sometimes competing roles (recreation, restoration, and research) for urban wetlands could coexist through thoughtful planning, although for obvious reasons the supporters of these sometimes competing uses can sometimes clash.
Studies have shown that urban residents value having wetlands nearby, in keeping with other research that shows that urban residents prize having natural environments near their residences. This proximity can even help to boost property values (leading at times to environmental justice issues when access to these areas is denied to poorer residents of cities).
But our urban wetlands are under tremendous pressure, often stemming from two closely-related threats: the conversion of wetlands to urban areas and the increased stress wetlands face due to hydrological changes in urban area (cities drawing water from wetlands to provide for their needs, or, conversely, discharging larger amounts of water due to increased impervious surface area, increased aquatic pollution, and so on).
The Ramsar Convention seeks to protect urban wetlands, just as it does wetlands in more rural areas. It even created an accreditation system for World Wetland Cities, where cities can apply to be given that title. At the same time, some researchers have pointed out that the Convention wasn’t ideally created to deal with urban wetland conservation, the focus in the early 1970’s being much more on rural wetlands. Hettiarachchi, Morrison, and McAlpine, 2015, for example, point to several weaknesses, including a lack of focus on environmental justice and and not enough recognition of the complex social, economic, ecological, and political systems to be found within cities. They then offer some interesting modifications that could address these shortcomings.
In urban areas (and perhaps elsewhere), the hands-on wetland conservation activities (as opposed to the equally important education and legislation activities) can be split into two broad categories:
- Protecting existing, intact wetlands: This is perhaps most true in rapidly spreading and growing cities, but also true for remnant wetlands in more established cities that aren’t spreading out as much.
- Restoring degraded wetlands: Wetlands that have already been degraded – or even destroyed – in urban areas are often the target of restoration or creation efforts. Sometimes these efforts focus on restoring the ability of the system to provide ecosystem services to the city, sometimes for habitat preservation and creation, sometimes for recreational/educational purposes, and sometimes for all of the above reasons – and possibly even more. David Pettit of the NRDC wrote an interesting blog post about wetlands restoration and creation projects in LA, as a good example.
So Happy World Wetlands Day (er…week?)! Next time you pass by a partially-submerged piece of land in an urban area, give it a wave.
(As a bonus, check out these satellite images of some of our world’s wetlands, courtesy of the European Space Agency!)
Boyer, T. and Polasky, S. 2004. Valuing urban wetlands: A review of non-market valuation studies. Wetlands 24(4): 744-755
Hettiarachchi, M., Morrison, T.H., and McAlpine, C. 2015. Forty-three years of Ramsar and urban wetlands. Global Environmental Change 32: 57-66
Mahan, B.L., Polasky S., and Adams, R.M. 2000. Valuing urban wetlands: A property price approach. Land Economics 76(1): 100-113
Zedler, J.B. and Leach, Mark K. 1998. Managing urban wetlands for multiple use: Research, restoration, and recreation. Urban Ecosystems 2: 189-204
Finally! We had snow, after a snow-starved winter. And it wasn’t just a couple of inches, no. Up at our house we had about 25 inches of the good white stuff.
There were so many photos to choose from this week — everything was gorgeous both during the storm and after. Seriously, I had a really hard time deciding this week!
For all of you who were caught up in #Snowzilla2016, I hope you had as much fun as I did!
We finally have winter! We’re in the midst of a blizzard here in DC today. I love snow, so this is absolute heaven for me (yes, even though it requires some shoveling). Next week I’d imagine you’ll be seeing a snow photo, but the storm arrived too late for this week’s picture. Week Nine’s photo is of ice that formed over a tributary of Rock Creek. It was a thin layer of ice with moving water underneath (well, a little — the stream is not very deep right there), but I loved the patterns and textures of the ice.
For everyone on the East Coast, enjoy the wintery weather and stay safe!
It’s that annual day when we get to pay our respects to our neighbors with the fuzzy tails! We’ve had a couple of black squirrels living near us this year, and often see one of them running down the fence that separates our neighbor’s yard from ours in the morning (there’s a great story about DC’s black squirrels that I’ll tell some other time).
I’ve written about the history of DC’s squirrels before, as well as about urban squirrels in general. And looking back, it turns out that when I wrote about Squirrel Appreciation Day in 2012 it was on the eve of that winter’s first big snow storm! And here we are on the eve of our first big snow event this year, too (and it looks like it’ll be a big one). Coincidence? Maybe we should ask our furry friends.
Oh, and don’t forget this amazing photo. Cheers!
A new paper (Ives et al., 2016; see citation below) discusses the important role urban areas can play in Australian biodiversity conservation. The authors compared the distributions of Australia’s threatened plants and animals to the area covered by 99 cities in Australia. They also created “dummy” cities in the same areas to make sure that their results weren’t skewed if cities were found in particularly diverse bioregions.
The authors claim that this is the first study to show (at least at the “continental scale”) that urban areas can not only be biodiverse, but that they can contain more threatened species per hectare than rural areas. This has huge implications for biodiversity conservation planning in general, which historically has omitted or at least given short shrift to urban areas (although this is changing quickly and for the better).
All of the cities they included (covering only 0.23% of the continent) either had or were likely to contain threatened species — and in fact a full 30% of Australia’s threatened species were found or likely to be found in these cities (the authors did control for other factors that might cause a high level of biodiversity).
Some species were restricted to urban areas. Perhaps not-surprisingly, this was more true for plants (who are not as able to move away as human disturbances increase) than animals. In fact, some endangered plant species’ ranges were exclusively in urban areas, demonstrating that cities might be tremendously important when it comes to plant conservation.
Species made use of different types of land in urban areas. Some relied on remnants of relatively untouched (and it’s all relative, to be sure) areas – again, many plant species fell into this category. Other species made use of modified landscapes. For example, the authors point out that the Carnaby’s black cockatoo uses human-created pine plantations in Perth. In general, they found that “nomadic and migrant” species (they cite in particular the grey-headed flying fox (Pteropus poliocephalus) and swift parrot (Lathamus discolor)) often relied on these human-modified resources as stable sources for food, given that humans tend to plant a variety of things and often supplement natural conditions by watering and otherwise tending to them.
There were a few caveats to their study. As many urban areas in Australia are relatively young, these cities may be carrying a so-called “extinction debt,” which might help account for their high biodiversity (the same might be true for US cities). In addition, they acknowledged that there is no agreed-upon definition of urban areas, so what some researchers might consider urban others might not. This needs to be remedied as urban-focused biodiversity conservation research grows.
But, no matter what sort of habitat and resources these species use, this study provides important evidence that cities need to be considered in conservation planning in general. Plus, it further demonstrates that Australia has some kick-ass urban wildlife!
Ives, Christopher D., Lentini, Pia E., Threlfall, Caragh G., Ikin, Karen, Shanahan, Danielle F., Garrard, Georgia E., Bekessy, Sarah A., Fuller, Richard A., Mumaw, Laura, Raynor, Laura, Rowe, Ross, Valentine, Leonie, and Kendal, Dave. 2016. Cities are hotspots for threatened species. Global Ecology and Biogeography, 25: 117-126.