SB 6.4.4
sri-suka uvaca
yada pracetasah putra
dasa pracinabarhisah
antah-samudrad unmagna
dadrsur gam drumair vrtam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Sukadeva Gosvami said: When the ten sons of Pracinabarhi emerged from the waters, in which they were performing austerities, they saw that the entire surface of the world was covered by trees.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
When King Pracinabarhi was performing Vedic rituals in which the killing of animals was recommended, Narada Muni, out of compassion, advised him to stop. Pracinabarhi understood Narada properly and then left the kingdom to perform austerities in the forest. His ten sons, however, were performing austerities within the water, and therefore there was no king to see to the management of the world. When the ten sons, the Pracetas, came out of the water, they saw that the earth was overrun with trees.
When the government neglects agriculture, which is necessary for the production of food, the land becomes covered with unnecessary trees. Of course, many trees are useful because they produce fruits and flowers, but many other trees are unnecessary. They could be used as fuel and the land cleared and used for agriculture. When the government is negligent, less grain is produced. As stated in Bhagavad-gita (18.44), krsi-go-raksya-vanijyam vaisya-karma svabhava jam: the proper engagements for vaisyas, according to their nature, are to farm and to protect cows. The duty of the government and the ksatriyas is to see that the members of the third class, the vaisyas, who are neither brahmanas nor ksatriyas, are thus properly engaged. Ksatriyas are meant to protect human beings, whereas vaisyas are meant to protect useful animals, especially cows.