Hurricane Effects on Urban Arthropods
The frequency of extreme weather events is predicted to increase with global climate change. Hurricane Sandy devastated New York City with high winds, rain, and a massive storm surge. The human and economic toll of this storm was record-breaking but the ecological toll is unknown.
Arthropods, such as insects, spiders, and millipedes, are the most abundant and diverse animals in cities. We had been sampling the arthropod communities present in NYC parks, road medians, and trees for several years before Sandy, then went back to resample those communities in 2013.
Our goal was to understand how Hurricane Sandy changed ground-dwelling and tree-dwelling arthropod communities in New York City and how those changes affected the services or disservices they provide. Specifically, we wanted to know:
1. How did prior exposure to chronic environmental stress affect communities’ response to Hurricane Sandy in New York City?
Many urban arthropods live in stressful habitats, such as road medians, but also in less stressful habitats, such as parks.
Ecological theories predict that communities living in stressful habitats are already “tough” and should be more resilient to disturbance than communities in less stressful habitats.
2. Do native and exotic species respond differently to the combined effects of chronic stress (such as living in a road median) and acute disturbance (such as Hurricane Sandy)?
Ecological theories predict that exotic species should be more abundant and native species less abundant in chronically stressed habitats.
We expected that, after the hurricane, even low-stress habitats (parks) would be increasingly colonized by exotic arthropods.
3. How does urban habitat and storm disturbance affect refuse consumption by urban animals?
In this part of the project we examined consumption of littered food waste by arthropods. This ecosystem service is relevant to urban public health and esthetics but has never been studied. No one has asked, “What happens to food we drop on the street?”
Theory and data from natural systems predict that in habitats with more biological diversity, more food should be eaten. In natural habitats, eating more “food” means more herbivory or predation. Although cities are not natural habitats, we wanted to know if the same principles apply to a common urban food source: littered food garbage.
We measured food removal by placing cookies, potato chips, and hot dogs in Manhattan street medians and parks. At the same sites, we assessed ground-arthropod diversity and environmental conditions, including flooding during Hurricane Sandy prior to the study.
What did we find?
Parks were clearly more diverse than medians. We encountered, on average, 11 hexapod families and 5 ant species per park sample, compared to 9 families and 3 species per median site.
Counter to our diversity-based prediction, however, arthropods in medians removed 2–3 times more food per day than did arthropods in parks. Surprisingly, flooding had little effect on arthropod communities or food removal.
Instead, one big eater seemed to be driving food removal. That was the introduced pavement ant (Tetramorium sp. E). When this species was present, more food got eaten. In some cases, arthropods consumed nearly as much food as vertebrates.
We estimate that arthropods alone could remove 4–6.5 kg of food per year in a single street median, reducing its availability to less desirable fauna such as rats. Thus, even small green spaces such as street medians provide ecosystem services that may complement those of larger habitat patches, like parks, and help keep cities clean.
Read the full story:
Youngsteadt, E., Henderson*, R. C., Savage, A. M., Ernst, A. F., Dunn, R. R. and Frank, S. D. (2014), Habitat and species identity, not diversity, predict the extent of refuse consumption by urban arthropods. Global Change Biology. doi: 10.1111/gcb.12791. PDF