Tag Archives: urban ecology

habitat area and fragmentation

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I gave a talk this week on a niche topic involving plant selection for stormwater management features like rain gardens in cities. I had just one slide on habitat connectivity and fragmentation as an interesting area for further research. That one slide generated a lot of interest. And it is an interesting topic. First of all, it has been looked at quite a bit in the design of nature reserves, but not so much in urban areas or areas with a mix of wild, agricultural, and urban land uses. And second, there is always the debate about whether focusing too much on connectivity metrics can detract from just preserving enough total habitat. The article below is an entry relevant to this question, relevant in the context of forests. In urban areas, in my view, this question gets flipped on its head. Fragmentation and disconnection is the de facto state, and can only be reversed on the margins. So the interesting question to me is what policy choices can make it the least bad. There is also the possibility that better policy choices in urban areas can reduce friction of (animal and plant) movement between wild landscapes, and even whether they can serve as relatively biologically functional islands in depleted agricultural landscapes.

Why controlling for habitat amount is critical for resolving the fragmentation debate

The need for a consensus on the effects of fragmentation per se is increasingly recognized (Miller-Rushing et al., 2019; Riva, Koper, et al., 2024; Valente et al., 2023) because deforestation continues and small forest patches are particularly vulnerable to destruction (Riva et al., 2022). If fragmentation per se reduces biodiversity, then policies should prioritize protection and restoration of large patches. If not, then policies should include all forest, irrespective of patch sizes (Riva & Fahrig, 2023). This would allow effective biodiversity conservation, even in human-dominated regions where no large patches remain, by protecting and restoring sufficient forest over a network of many small patches (Arroyo-Rodríguez et al., 2020).

2025 gardening books

Here is a roundup of recent gardening books from the Joe Gardener Podcast. I like to do a gardening book around January each year so this will give me some new ones to think about. Yes, you can accuse me of being mostly an armchair gardener if you want. I have a garden but I take a mostly laissez-faire approach, especially this past year when work, school, family, and life have conspired to take up 150% of my available time (outside of sleep and eating, two things I never skimp on.) Here are a few that caught my eye:

  • How Can I Help – a new one on ecological gardening from Doug Tallamy
  • Nature’s Action Guide by Sarah Jayne – sounds kind of similar actually
  • Several books on seed saving, a topic I have always been interested in.
  • Fruit Tree Pruning: The Science and Art of Cultivating Healthy Fruit Trees by Susan Poizner – I have two fruit trees. They grow a significant amount of Asian pears and persimmons each year. This makes the neighborhood squirrels very happy.
  • The New Organic Grower: A Master’s Manual of Tools and Techniques for the Home and Market Gardener by Eliot Coleman – a classic. I used to have a copy when I was young and thought I might grow up to live on a piece of land and have some time on my hands. Which I remember asking a bookstore to order for me before Amazon or even the internet existed.
  • Plant Grow Harvest Repeat by Meg McAndrews Cowden – “the book on succession planting”
  • The Vegetable Gardening Book: Your Complete Guide to Growing an Edible Organic Garden from Seed to Harvest by Joe Lamp’l – the podcast guy
  • Attracting Beneficial Bugs to Your Garden by Jessica Walliser – pretty self-explanatory right?

biodiversity decline

Out of many doom and gloom topics, biodiversity decline may be the gloomiest, or at least the gloomiest that the global political system and public by and large are not thinking about. With climate change, at least we all know something is going on even if we are bickering about it and not doing enough 50 years after we needed to start acting in a concerted way. Anyway, global insect decline is just beyond shocking. Here is just one article hot off the presses:

Long-term decline in montane insects under warming summers

Widespread declines in the abundance of insects portend ill-fated futures for their host ecosystems, all of which require their services to function. For many such reports, human activities have directly altered the land or water of these ecosystems, raising questions about how insects in less impacted environments are faring. I quantified the abundance of flying insects during 15 seasons spanning 2004–2024 on a relatively unscathed, subalpine meadow in Colorado, where weather data have been recorded for 38 years. I discovered that insect abundance declined an average of 6.6% annually, yielding a 72.4% decline over this 20-year period. According to model selection following information theoretic analysis of 59 combinations of weather-related factors, a seasonal increase in insect abundance changed to a seasonal decline as the previous summer’s temperatures increased. This resulted in a long-term decline associated with increasing summer temperatures, particularly daily lows, which have increased 0.8°C per decade. However, other factors, such as ecological succession and atmospheric elevation in nitrogen and carbon, are also plausible drivers. In a relatively pristine ecosystem, insects are declining precipitously, auguring poorly for this and other such ecosystems that depend on insects in food webs and for pollination, pest control, and nutrient cycling.

For a more general overview of the insect decline issue, I suggest this paper: Insect decline in the Anthropocene: Death by a thousand cuts.

There is some debate about which causes are more important than others, but like climate change, the causes are pretty much known (and one of them is climate change). Destruction of natural ecosystems to clear land for urban areas and agriculture is the biggest and most obvious. Massive use of pesticides and other agricultural chemicals. Heat and drought. The spread of invasive species.

The destruction of nature is just sad for everyone who values nature for its own sake. For those who don’t, it’s a little harder to come up with the elevator pitch for why this matters. Pollination has huge and obvious economic value, but maybe we can replace natural pollinators with domesticated bees for the most critical crops.

Beyond pollination, insects are the base of the food chain. Their disappearance is actually a symptom of loss of plant life, since many of them are herbivores and depend on plants. We should be able to help a little bit just by conserving or replanting some of the native trees and other plants we know they depend on in our urban areas and on farms. A guy I know wrote a paper about this.

Insects, in their function as herbivores, are also critical in transferring energy, biomass (i.e. carbon), and nutrients up the food chain to everything from birds to amphibians to fish. So their loss is a direct cause of the loss of a lot of these other animals. But in terms of the food supply, we can probably produce chickens and pigs and cows without them I suppose. So it’s a little hard to tell that “conservative” uncle at the Thanksgiving table that there is some imminent tipping point where the bugs dwindle to a certain level and then we all starve to death. (“Conservative” is in quotes because a true conservative would be interested in, well, conserving things not destroying them.)

unifying “Green Area Factor” and “No Net Loss of Biodiversity” measures

Here in the US, implementing these types of policies seems mostly like a political pipedream at the moment. I could imagine a really smart developer doing this as a marketing scheme, maybe. maybe. But this is a great article that gives us a window into some things that are being tried in Europe (although, I also hear voices in Europe speaking longingly of the perceived lack of regulation in the US). I don’t know – our regulations may be equally strong or stronger in some areas like hydrology and water quality (which is missing from the framework discussed here btw) wetland and floodplain protection, and endangered species (although these are under constant political threat). Ideally in my view, species would not have to get endangered first before we will do anything for them.

More than the sum of its parts – Integrating the use of green area factor tool and biodiversity offsetting for no net loss urban planning

As part of the actions to fight biodiversity loss, the European Union is working on a restoration regulation demanding the principle of no net loss (NNL) state of biodiversity of urban green space. Applying this principle in urban planning may raise conflicts between biodiversity conservation and ecosystem services provision. Furthermore, integrating the NNL of biodiversity principle into urban planning cannot be isolated from existing planning tools or processes. Here we present a novel approach where the green area factor tool and biodiversity offsetting are integrated to achieve NNL of biodiversity in urban planning, while maintaining the necessary ecosystem services and avoiding the negative, unintended tradeoffs that may occur if only one of these tools is used in the planning process. We provide a model which combines the two approaches to create a holistic method to understand and govern both biodiversity and ecosystem services of urban greenery. The model is intended to be used as part of urban planning processes.

potential natural vegetation

This is a short Wikipedia article about defining and mapping the historical or potential natural vegetation of areas that have been developed or otherwise altered by humans. Sure, there is plenty of scientific debate about the concept but it seems to me like it could be adapted for practical purposes. Even in the U.S., we have ordinances in most places requiring maintenance or restoration of something approaching natural hydrology on development sites (I’m not saying implementation of this concept is remotely perfect either, just that it is widespread and more or less accepted). But we don’t have anything approaching that for ecology, and you can restore hydrology without restoring an ecosystem (for example, with a storage and infiltration tank under a parking lot). So if you have a model of what the original or potential natural vegetation of a place is, you should be able to quantify what percentage of that is being destroyed, preserved, or restored by a given project.

This is just some natural(ish) vegetation. I’m just trying to make the site more visually interesting, okay? Thank you Indiana Jo for posting on Wikimedia.

roots = more infiltration

The presence of growing plant roots and organic matter will increase the rate water can move into the soil. We all know this from elementary school, right? Right? Well, some adult professionals are unfamiliar or skeptical. I won’t call out any of my fellow civil engineers by name.

The Effect of Herbaceous and Shrub Combination with Different Root Configurations on Soil Saturated Hydraulic Conductivity

Information on the effects of differences in root and soil properties on Saturated hydraulic conductivity (Ks) is crucial for estimating rainfall infiltration and evaluating sustainable ecological development. This study selected typical grass shrub composite plots widely distributed in hilly and gully areas of the Loess Plateau: Caragana korshinskii, Caragana korshinskii and Agropyron cristatum (fibrous root), and Caragana korshinskii and Artemisia gmelinii (taproot). Samples were collected at different distances from the base of the shrub (0 cm, 50 cm), with a sampling depth of 0–30 cm. The constant head method is used to measure the Ks. The Ks decreased with increasing soil depth. Due to the influence of shrub growth, there was significant spatial heterogeneity in the distribution of Ks at different positions from the base of the shrub. Compared to the sample location situated 50 cm from the base of the shrub, it was observed that in a single shrub plot, the Ks at the base were higher, while in a grass shrub composite plot, the Ks at the base were lower. Root length density, >0.25 mm aggregates, and organic matter were the main driving factors affecting Ks. The empirical equation established by using principal component analysis to reduce the dimensions of these three factors and calculate the comprehensive score was more accurate than the empirical equation established by previous researchers, who considered only root or soil properties. Root length density and organic matter had significant indirect effects on Ks, reaching 52.87% and 78.19% of the direct effects, respectively. Overall, the composite plot of taproot herbaceous and shrub (Caragana korshinskii and Artemisia gmelinii) had the highest Ks, which was 82.98 cm·d−1. The ability of taproot herbaceous plants to improve Ks was higher than that of fibrous root herbaceous plants. The research results have certain significance in revealing the influence mechanism of the grass shrub composite on Ks.

how to get rid of robins???

In my experience, robins can tear up grass, scatter mulch while foraging for food, and even eat fruit or crops from your garden. Moreover, their nests can harbor parasites and insects, which can put your family, pets, and home at risk. The smell of robin droppings can also be incredibly unpleasant, particularly if the birds manage to get inside your walls.

todayshomeowner.com

This left me speechless – It honestly never occurred to me that robins could have enemies. Could this person maybe be thinking of pigeons? Or is this person even a person? If this is an AI concluding that a harmless bird is a threat that needs to be gotten rid of, it may be a cautionary tale for other species, like ours.

March 2024 in Review

Most frightening and/or depressing story: Ralph Nader says the civilian carnage in Gaza is an order of magnitude worse than even the Gaza authorities say it is. Which is almost unthinkably horrible if true, and makes the Israeli public statements about collateral damage seem even less credible. However even handed you try to be in considering this war could be a proportionate response to the original gruesome attack, it is getting harder.

Most hopeful story: Yes, there are some fun native (North American) wildflowers you can grow from bulbs. Let’s give the environmental and geopolitical doom and gloom a rest for a moment and cultivate our gardens.

Most interesting story, that was not particularly frightening or hopeful, or perhaps was a mixture of both: I looked into Belarus, and now I am just a little bit less ignorant, which is nice.

native wildflowers from bulbs

For something random and different (but hey, it’s meteorological spring right?), here are some wildflowers native to the U.S. that can be grown from bulbs.

  • Blue-eyed grass (Sisyrinchium atlanticum), native to eastern North America
  • Calochortus spp. lily, native to western NA
  • Dwarf-crested iris (Iris cristata), native to eastern NA
  • Fritillaria spp., native to western NA
  • large camas (Camassia leichtlinii), native to western NA
  • Nodding onion (Allium cernuum), native throughout US
  • Northern spiderlilly (Hymenocallis occidentalis var. occidentalis), southeastern US
  • Rain lily (Zephyranthes atamasca), southeastern US
  • trout lily (Erythronium americanum), central and eastern US
  • Turk’s cap lily (Lilium superbum), central and eastern US
  • Ookow (Dichelostemma congestum), western NA
  • Wood lily (Lilium philadelphicum), throughout NA

It’s nice to grow plants from seed for genetic variety, but bulbs certainly have their place. It’s good to know there are good native choices (well, I don’t know if these are choices down at my local Lowes/Home Depot, but they should be).

census reveals massive Philadelphia population loss – for pigeons

The (paywalled) Philadelphia Inquirer reports on a citizen science bird count showing a massive drop in the pigeon population over the last few years. At the same time, raptor populations like red-tailed hawks and Peregrine falcons are up. There are reasons the data are uncertain, but this is still pretty cool.

I’ve had some memorable raptor sitings in Philly over the years. Recently, I heard a significant commotion and looked up to see a red-tailed hawk in a tree very close to my front door. This was early spring before there were leaves on the trees, so I imagine it had a good line of site to the ground. Mice and rats were the first prey species that popped into my mind, but yeah there are pigeons around too.

Peregrine falcons are not very shy in urban environments. I remember seeing one sitting on a street map above a busy street, next to a park that I know from personal experience is full of mice, rats, and pigeons.

Once I saw a falcon that had trapped a squirrel under a bench in Rittenhouse Square. Like I said, they are not shy around people, but when the park is busy they will tend to be hire up in the trees or on buildings. This was very early in the morning, and the falcon was just sitting there on the bench with the squirrel underneath. The squirrel would try to run out, and the falcon would swoop out and try to get its talons around the squirrel, and the squirrel would slip out and dart back under the bench. Falcons are big birds. I gave this one a respectful distance, but it took no notice of me whatsoever.