How does drought and overgrazing degrade the soil?

Drought and Overgrazing: When drought conditions persist in agricultural areas, it can lead to overgrazing of watershed lands, as there is not enough vegetation to support the normal grazing habits of livestock. Overgrazing can occur when there is not enough vegetation to support the normal grazing habits of livestock, and animals are forced to graze on smaller areas of land more intensively. This can lead to soil degradation, as the soil is subjected to increased trampling and erosion.

Hydrophobic Soil: As the soil becomes degraded, it can become hydrophobic, meaning that it repels water rather than absorbing it. This can lead to flash flooding, as the water is unable to infiltrate the soil and instead runs off the surface, causing erosion and carrying sediment and debris with it.

Flooding and Silt Transportation: Silt transportation can also occur as a result of soil degradation and flash flooding. When the soil is not able to absorb water, it can become loose and prone to erosion. As the water flows over the surface, it can carry the loose soil with it, leading to silt transportation. This can cause problems downstream, as the increased sediment load can cause rivers and streams to become more shallow and narrow, leading to increased erosion and potentially even more flash flooding.

Drought and overgrazing can lead to significant soil degradation in Hawaii. Drought, land degradation, and desertification, combined with human activity and environmental changes, cause important soil losses and a reduction in natural fertility. Overgrazing can reduce ground cover, resulting in increased soil temperatures and evaporation rates, leading to soil hydrophobicity. This can cause water infiltration problems and further reductions in available forage, leading to a vicious cycle of soil degradation. In addition, overgrazing can cause soil compaction and sediment loss, which can further reduce soil fertility. Sustainable grazing management can help reduce the impacts of drought and overgrazing by increasing the flexibility and resiliency of operations.

 

Further reading:

Managing Effects of Drought in Hawai’i and U.S.-Affiliated Pacific Islands https://www.fs.usda.gov/research/publications/gtr/gtr_wo98/gtr_wo98_chapter5.pdf

A Century of Drought in Hawai‘i: Geospatial Analysis and Synthesis across Hydrological, Ecological, and Socioeconomic Scales https://www.fs.usda.gov/psw/publications/giardina/psw_2022_giardina008_frazier.pdf