I don't really see it as a fixed amount of work that needs to be distributed among all the people. Getting more half moons dug in a shorter amount of time will reclaim a lot more farmland, and will have labor opportunities in actually working the land.

Digging out the half moon, one per person per day, is only the start. These communities are trying to actually grow crops, too. So it seems that if you have a pool of labor available, the upper limit is going to be how much agricultural land area can be managed by that labor pool. At that point digging more half moon patches isn't going to create any more opportunities (unless we're talking about improving the agricultural productivity per worker, and should probably talk about farming equipment too). If the income is to come from the crops they produce, shouldn't increasing the output of crops be economically good for that community?

It seems that using equipment would transform a larger quantity of land, which is good for the environment in general. Then, the economic impact would still be distributed among the entire workforce, able to work that land and do the actual agriculture.

What am I missing?