Are cities at risk of losing squirrels?

This review is part of a special collaboration between Planetizen and Booked on Planning, a biweekly podcast where AICP planner Stephanie Rouse and Jennifer Hiatt chat with authors of the latest books shaping urban planning today. Listen to the episode with today’s author in the player below. 

Squirrels are an often-overlooked contributor to our cities. You may have a love/hate relationship with them — or, if they terrorize your garden like they terrorize mine, you may fall squarely in the hate corner — but their contribution to healthy ecosystems and forest development almost makes up for this behavior. Author Nancy Castaldo aims to make the case for the humble backyard creature in her book "Squirrel: How a Backyard Forager Shapes Our World."

U.S. cities have not always been home to these bushy little foragers. They were introduced to urban parks in the 19th century. In May 1847, three squirrels brought in from the countryside were introduced to a new square-turned-park in Philadelphia. Other cities, including Boston, New Haven and New York City, soon followed suit.

Then as now, not everyone was enthusiastic about the new residents spreading throughout their cities and, in some instances, the introduction of a new squirrel population came at the cost to the native squirrels. Grey squirrel introduction in European countries has actually been a "symbol of a species that is 'flattening diversity.'" To attempt to reset the balance, in 2006 London restaurants were putting the invasive grey squirrels on the menu.

But when at home in their native habitats, squirrels contribute positively to their surrounding environments. They lose track of many of the nuts they bury in the fall, leading to new tree growth in the spring. Their digging habits help produce good soil health. That is why it’s dangerous to ignore the signs that this unobtrusive, quotidian animal is in need of study. Castaldo cautions that "without knowing the full status of a species, it seems impossible to manage it properly." Squirrels are such a common sight that they rarely get the research attention they deserve, leading to a lack of understanding around their population health and the negative impacts on the ecosystem should they become endangered.

There are already signs that all may not be well in squirrel-land because of biodiversity loss and changing climate conditions. But, as in the past, the ability of the squirrel to adapt and change in response may be what saves it. Without proper data to understand whether this is occurring, it will be impossible to know whether or when to step in and help. Community members can assist scientists in collecting population data when funding for or documenting squirrel locations through the iNaturalist app.

While the book doesn’t set forth action items for how to address the squirrel population in our cities, Castaldo's goal is rather to bring attention to this overlooked species and call out the need for better data. Once this has been addressed, better planning can be undertaken to ensure the chatter we are so familiar with in our backyards and parks doesn’t go silent.