America is fast becoming a pop-up nation. From sea to shining sea, her cities have been swept up in the frenzy for temporary architecture: Brooklyn vendors sell their wares in artfully arranged shipping containers; Dallas's Build a Better Block group champions DIY painted bicycle routes and pop-up small businesses; architects in San Francisco are repurposing metered parking spaces into miniature parks; residents in Oakland, California rallied to create an entire pop-up neighborhood. The phenomenon has even climbed its way from grassroots origins to the agendas of local authorities: D.C.'s office of planning sprouted a Temporary Urbanism Initiative, while New York’s transportation commissioner Janette Sadik-Khan is implementing what she calls "Jane Jacobs’s revenge on Robert Moses" with her fast-acting interventions favoring pedestrians and cyclists. The temporary, so it seems, is overtaking the permanent. But how permanent is our current fascination for the temporary?

There is a natural tension within the term "temporary architecture" that makes the notion seem vaguely unstable. To understand the significance of this fact, it helps to go back to the lessons of Vitruvius. The prolific architect and scribe of antiquity imparted three principal virtues, among other things, unto the Western architects that would fall under his influence: utilitas, firmitas, and venustas. The meaning of these terms is subject to much debate, but semantics aside, Vitruvius's virtues roughly translate to "utility," "durability," and "beauty." With these virtues firmly in place, Vitruvius equated the Roman empire's commanding marble cities with built perfection. The monuments that he extolled in the 1st century BC are an unmistakable tribute to the import of permanence.

But for centuries now, this association of great architecture with fixed and timeless permanence, along with the entire Vitruvian triad, has been losing traction. Our environment has been built, altered, and rebuilt in overlapping waves. While some buildings stand the test of time, most seem to expire in relevance. Grand architectural and planning schemes are increasingly rare. In fact, we fast-forward to today, and it seems that we are collectively swinging towards a polar opposite of Vitruvian values. We are moving towards an architecture in which the permanent is becoming a lot less permanent.

Lydia DePillis, architecture and urban issues critic for the Washington City Paper, recently penned an article entitled "Temporary is the New Permanent." Her piece centers around a recent urban intervention in D.C., in which, for one weekend, a typically lifeless neighborhood in D.C. became the site of a bustling marketplace. People (white people, as DePillis emphasizes) flocked to the remote district by bicycle to sample food truck fare, listen to live music, and admire the work of local artists and artisans. The next Saturday, the streets were empty, as if it were all a dream. But when night fell, an entourage of D.C. youth came flooding into the area on chartered school buses to kick off a three-month-long arts event series called LUMEN8Anacostia.

This pop-up urban revival is but one example of an approach informally called "lighter, quicker, cheaper" (LQC) by members of New York’s Projects for Public Spaces (PPS). The organization pitches the phenomenon as a response to the strains of contemporary urban living: "As cities struggle to do more with less… we have to find fast, creative, profitable ways to capitalize on local ingenuity and turn public spaces into treasured community places." Enter the new triad of virtues: the light, the quick, and the cheap.

The LQC approach favors low-cost projects, incremental steps, and high levels of community engagement. Its implementation is widespread, ranging from pop-up marketplaces and pavilions to seemingly cosmetic but effective city planning reforms. Small budgets meet less resistance and allow for faster execution, which means the effects of these interventions can be felt more immediately. As a result, the schemes can be adapted as needed, responding quickly to the successes or failures of their forms. Moreover, these projects are often initiated by locals, diverse groups of individuals who can see the demands and aspirations of their respective communities firsthand. The results often become a more direct and intimate response to their sites.

Because of its low cost, modest appearance, and community-driven spirit, LQC architecture is often seen as a reflection of our times: this sudden infatuation for the temporary can be read as a pragmatic response to economic downturn as well as a material expression of the slow democratization of our cities.  But if and when current circumstances change, will cities abandon the temporary for more traditional solutions?

That is a difficult question to answer, as our conceptions of architecture are becoming increasingly unfixed. It seems that today’s architects, planners, and city dwellers are actively redefining the binary that distinguishes the temporary and the permanent. As we are seeing more and more, temporary architecture can be surprisingly permanent; Brooklyn's DeKalb Market and Oakland's Popuphood are two examples of essentially permanent interventions cloaked in the illusion of impermanence. Both projects are seen as "temporary" not because they are disposable, but because they are susceptible to instantaneous change at multiple points in time.

Conversely, temporary architecture that is objectively short-term but nonetheless strives for an illusion of permanence can be a thoroughly wasteful endeavor. Temporary, in this throwaway sense, risks enabling architects to disregard the specifics of their sites and build freely and thoughtlessly. The flippant pavilions and overwrought month-long constructions that result are not responsive to our times. Instead, they perpetuate the older, static notion of permanence, which has its place elsewhere. At their worst, these short-lived projects cling to an architect or patron's self-serving delusions of grandeur, and the public is left with only a burn image of a monument, a two-dimensional idea that can occasionally inspire but often merely conceals a serious drain on efforts and resources. With all this in mind, we can return to our initial question: Is the pop-up here to stay? That depends on whether the pop-up truly means to stay.

To see more images of the pop-up urban interventions mentioned in this piece, click on the slide show.