You village isn't doomed, but you might have some tense moments, especially if your population is higher than approximately 15 villagers (which is what the farm can comfortably support). You should gather every mushroom you can find to get the food supply up as high as possible, which will help avoid starvation. You should also have every adult villager working at the research table whenever the farm is empty, so that you'll be able to get the next food technology. If your villagers start getting weak from hunger, there's a stew that you can make that will restore their health. If you don't want to experiment with the stews, there are recipe books in the Guide section for the game.

If that ever happens again, you can check the game log to find out why they got low on food. Usually it's due to sick farmers that didn't get healed, but there can be other causes, too. To find out about the log, check the sticky post mear the top of this forum.