The Jewish High Holidays, which begin at sundown tonight, celebrate the turning of the calendar with symbolic foods (apples and honey to signify a sweet new year) and ask the observant to reflect on their actions. Sermons by rabbis often touch on issues of social justice, including the environment, and ask congregants how their choices in those realms do — or do not — represent Jewish values.

So what better time to ask: Is keeping Kosher good for the environment? Turns out, the green perks of keeping kosher are sometimes offset by what's eaten instead of no-nos like pork and shellfish, Emily Gertz reports.

Pork-free diets heavy on chicken and beef produce 6 percent more greenhouse gas emissions than those split between the three, she writes. But catching herring or salmon requires less fuel than trawling for shrimp, making kosher the more ecofriendly choice when it comes to seafood. (Tuna is an exception, she notes.)

But the question of green food choices isn’t limited to the world of kosher and halal, Islamic dietary law. (About 30 percent of the 10.2 million Americans who eat kosher are Muslims whose dietary restrictions overlap those of kosher-keeping Jews, Gertz notes.) The issue is complicated for anyone who eats: food that travels thousands of miles by plane or truck from the grower to your refrigerator adds to its carbon footprint, or how much carbon dioxide it produces. And some have argued that organic farming produces more pollutants than conventional agricultural practices by requiring more animals or seed to yield the same harvest as cows or vegetables that are traditionally grown with antibiotics or pesticides.

Need more environmental angst to mull over in shul tomorrow? Check out Earth 3.0. Drilling, solar power and other energy dilemmas that are taking center stage on the presidential campaign trail offer plenty of food for thought over your kosher, organic brisket. Gut yontif!

(Image of Reuben — not kosher because it mixes cheese and meat — from iStockphoto/Andrea Skjold)