Natural Sequence Farming

Gidday all
Since i have dug a few water diversion trench's i have noticed that quiet a few yabbies have moved into them and dug a few houses along its length.
Would i be correct in assuming that if they are there then the ground has got enough moisture in it and that they would over time improve the fertility of the ground in which they live?
Any thoughts.

greg

Thanks Insight
so the more they take up house the better the ground should become?
Thanks again

Greg