By Paul Reidinger

BIG CITIES TEND to be Green, of course, but they also tend to be (while not getting enough credit for being) green, with a small g. It is true that big cities are jungles of brick and concrete, rage and bad manners, exhaust and used syringes, but they are also places of tremendous, or potentially tremendous, environmental efficiency. City dwellers take up less square footage per person than suburban or exurban or rural dwellers. They don't have to travel as far to work and often, because of public transit, don't even have to drive. Population density also reduces the environmental costs of a wide spectrum of services, from delivering the mail to setting up farmers markets to running a waste-collection system that emphasizes recycling and composting. (There is a darker side to all this, having to do with unseemly human reactions to overcrowding, but that is another story for another day.)

Despite the massive physical imposition on the land that is any city, the land doesn't easily give up. You don't have to look very far around this town, at least, to find wild fennel popping up in sidewalk cracks, rosemary creeping around the bases of street trees, and wild raspberry canes beckoning in a Presidio breeze. Forage is an underpracticed urban art we may well wish we'd paid more attention to the next time an earthquake knocks out power, topples bridges, and otherwise upsets the extensive and intricate networks that bring food from faraway farms to city tables. In the meantime we have Urban Forage, a restaurant that, though not really dependent on urban forage, reminds us just by its name that living in a city does not and cannot mean abandoning our relations with nature.

Urban Forage also reminds us that the differences among vegetarians, vegans, raw-food aficionados, and live-food proponents are just as wide and deep – in some cases chasm-like – as those between omnivores and vegetarians. Dairy products are, for some of us, the sugar coating on the bitter pill of meatless food, and please excuse my brief outburst of metaphor-mixing. Cheese and butter, cream and eggs – spoonfuls of these help all those green and leafy medicines go down, though not at Urban Forage, which eschews them in favor of, in the main, nut pastes. Tahini, made from ground sesame seeds, is familiar, of course, as is peanut butter, and you will find sauces based on them deployed throughout the menu. But you will also find a pâté of ground walnuts, used as a spread and a topping, along with an ice-cream substitute concocted from cashew butter and coconut milk.

These innovations are fundamental to Urban Forage's menu, which occupies a range on the meatless spectrum between veganism and live food, and for the most part they are pretty successful. The ice cream, in particular, has the dense, creamy texture of the real stuff, and if it is a bit less sweet, so much the better. Sweet freaks can go with the fundae ($6.50), which adds a moist, wheat-free vegan brownie and chocolate (or strawberry) sauce for the total Dairy Queen, sugar-bomb effect.

The issue at Urban Forage is not about nut pastes, nor with freshness, setting, or service – all these meet a high professional standard – but with focus. Every dish needs an identity, and the architecture of spices and herbs is of heightened importance in meatless cooking, whose foundation of ingredients is narrower than in other culinary styles. How, then, to account for a dinner special ($10.95) of lentils seasoned with paprika, lemon, and thyme, then rolled up in cabbage leaves to resemble fat little cigars and served with a slaw of shredded red cabbage and carrot in a rice vinaigrette? Is this supposed to be a Mediterranean-style dish, a New World dish, an Asian dish? It is all of that, in a way, and nothing at all in another. Strong flavors can lead a dish, but they can also contend with other strong flavors, in which case the result is cacophony and incoherence.

I had much the same reaction to the black-bean party ($7.95), which pretty desperately wanted to be chili – it was even served with a square of dryish cornbread – but found itself traveling instead with marinated kale and tahini dulse dressing. Baffling, really, especially since it would have taken so little to turn the beans into excellent black-bean chili. And why the guac'n'chips ($5.95) was served with zucchini coins instead of the more traditional tortilla chips I cannot guess.

On the other hand, the dishes that are focused – and there are quite a few of them – are tasty and convincing. The manwitch ($5.95), a black-bean burger with caramelized onions and barbecue sauce, could easily be passed off at many a backyard Fourth of July barbecue. The Thai wrap ($4.95) substitutes a collard leaf for a pancake but otherwise deploys a strong panoply of Thai ingredients, from shredded daikon to cilantro to spicy peanut sauce. And the coatlique ($7.50) – essentially a tostada heaped with black beans, violet kraut, guacamole, pepper sauce, cashew sour cream, and cilantro – strikes its Mexican note with force and confidence.

Besides the main, sit-down location on Valencia near 16th Street (in a space little-changed from its brief turn last year as home to the Lunch Store), Urban Forage operates two take-out shops, one in the lower Haight and the other in the Castro. The emphasis on take-out might at least partly explain the tendency to bundle everything in finger-friendly wrappings, for urban foragers, like everybody else in the city, must often eat on the run, yet nowhere is it written that fast food cannot also be green, if not Green.

Urban Forage. 561 Valencia (at 16th St.), S.F. (415) 252-1000. Sun.-Thurs., 10 a.m.-10 p.m.; Fri.-Sat., 10 a.m.-11 p.m. No alcohol. MasterCard, Visa. Noisy. Wheelchair accessible. Take-out locations: 254 Fillmore (at Haight), S.F. (415) 255-6701; 415 Castro (at Market), S.F. (415) 861-2499.