One of the beautiful features of the Land of Israel is its wide-ranging topography. The lowest point on earth some 1,300 feet below sea level is mere miles from the hills of Jerusalem some 2,500 feet above sea level. Mountain ranges, desert, lush farmland, great gorges, hills and flatlands are in close proximity to each other - even within walking distance. When one adds in the tiny geographical size of Israel such is all the more remarkable - and makes environmental concerns all the more important. It is not by chance this Land was chosen by G-d and given as a gift to the Jewish people.
 
We must both work and guard the land, developing it and safeguarding it at the same time. Balancing the needs of the environment and the economy is not always easy but is a task we must aim to master. 
 
“One may not raise small cattle in the land of Israel.” (Bava Kamma 79b) This is an aspect of the mitzva of yishuv haaretz, the mitzva to settle the land of Israel. Sheep, goats and the like need lots of land upon which to graze - land needed for agricultural purposes. 
 
While large cattle such as oxen cause even more “damage” to the land, to ban those would be a “decree that could not be followed by the majority of the people.” The services these animals provide - plowing and transport to name a couple - make them invaluable. Additionally large cattle are less numerous and easier to watch and thus prevented from “wandering” too far afield. (see commentary of the Tiferet Yisrael to the Mishna) 
 
The Sages also allowed the import of small cattle thirty days before a festival when the demand for meat was high. The mitzva of simcha, of joy on the festival was best observed through the eating of meat (and drinking of wine) not to mention the offering of sacrifices during the Temple period. The sages also allowed the importing of sheep thirty days before the wedding of a child[1]. Even grazing was allowed provided it be done out in the forest.
 
In addition to whatever damage small cattle might cause to one’s own land there was an even greater fear that shepherds would let their sheep graze in the fields of others. It is most instructive that G-d first revealed himself to Moshe as he was “shepherding the sheep of Yitro in the desert.” (Shemot 3:1) Our Sages as quoted by Rashi note that Moshe went to the desert “to stay far away from robbery so that they not graze in the field of others.” 
 
Moshe was following in the path of Abraham, the founding father of Judaism. “There was a dispute between the herdsman of Abram’s livestock and the herdsman of Lot’s livestock” (Breisheet 12:7). Our Sages explain that their debate was triggered by Lot’s herdsman allowing their livestock to graze in the fields of others. With G-d’s having promised to give the land to Abram’s inheritors - of whom the only one at that point was his nephew Lot - the herdsman felt they had the right to graze in the entire land. That may have become true in the future but the land was not yet theirs and Abraham’s herdsman called them to task for what was at this stage robbery. 
 
It was this dispute that led to Lot and Abraham parting ways. Should we be surprised that immediately thereafter “G-d said to Abram after Lot separated from him, lift up your eyes and see from the place where you are, north, south, east and west. All the land that you see I will give to you and your descendants forever?” (Breisheet 13:14-15)
 
The Torah could not be clearer. Our claim to the land is based on ensuring that we ensure we lead our sheep in the most honest of ways. This is why Abraham was given the Land of Israel, why Lot was not and why Moshe was chosen to lead the people back to it [2].  
 
We can now begin to understand what on the surface is a rather enigmatic assertion. “Rabbi Yishmael said: My father’s family were from the baalei batim, householders of the Upper Galilee. And why was their property destroyed? Because they used to pasture their flocks in forests, and to judge money cases alone.” (Bava Kamma 80a) The Gemara specifically allows one to pasture in the forest and thus Rabbi Yishmael elaborates that there was a small field nearby owned by others and Rabbi Yishmael’s family would let their sheep graze in this small field on the way to the forest. That this would cause destruction of their property makes sense when and only when we understand that our claim to the land is dependent on ensuring our sheep not graze in the fields of others. 
 
Rabbi Yishmael adds a second reason for the huge financial losses his family suffered, namely that of judging monetary cases individually instead of with a court of three. That is really the flip side of allowing sheep to graze where they may. Both are common miscues made as we tend to downplay the significance of such losses to others. While litigants may agree to abide by a decision made by one decisions made alone are much more likely to be in error. Judging alone is only for the Holy One blessed be He.
 
Rabbi Yishmael’s family, householders in the Upper Galilee, were nice honest people. However they were not meticulously careful regarding their sheep - letting them graze on the way to the forest - and were willing to rely on justice that may not be quite as good as it could be. These may be relatively minor faults but our Sages - if not the baalei batim - had very exacting standards.
 
[1] The language of the Gemara is literally for one’s son. That is likely because in Talmudic times it was the father of the groom who would pay for the wedding feast.
  
[2] Not only does the Torah care deeply about how we treat our animals, it is even concerned, at least regarding Moshe how we treat inanimate objects. Moshe was denied entry to the land because he mistreated a rock! This idea is reflected in the universal practice to cover the challah when we make Kiddush lest it be embarrassed by not being the first bracha we make. Imagine to what extent we must go lest we embarrass human beings.