The State Similarity Index attempts to quantify how similar states are to each other relative to other states. The index is a statistically-based way to measure this. 20% of the index is based on geography. 12.5% of a state’s geography score (2.5% of the overall State Similarity Index score) is allocated for the characteristics of a state’s land cover. The following factors were included in the calculation:
Forested Land
Maine is the most densely forested state. Tree canopies cover nearly 90% of the state’s land. Maine’s mountainous terrain and low population density have helped keep the state’s forests intact. In contrast, North Dakota, another state that borders Canada, has the lowest percentage of forested land in the United States. Less than 2% is tree covered. The state was originally mostly grassland, but now is used for cropland and pasture land. States in the Appalachian Mountains tend to be the most forested, while states in the Great Plains tend to have the lowest percentage of forested land.
Crop Land
Iowa has the highest percentage of farmland in the United States, with about 85% of its land area used for agriculture. The state’s fertile soil and favorable climate for crops have made it a leading producer of corn and soybeans. In contrast, Alaska has the lowest percentage of farmland, with only 0.1% of its land area used for crops. The state’s harsh climate and rugged terrain make it difficult to grow crops. States in the Midwest and the South tend to have more cropland than the Northeast and West regions.
Pasture Land
Pasture lands consist of natural grasses used for grazing animals, in contrast to crop lands that are regularly planted and cultivated to maximize the yield of food. Wyoming, Nevada, and New Mexico, three states in the West region, have the highest percentage of pasture land. However, there are many states that also have little pasture land, including New Jersey and Rhode Island, the most densely populated states, and Alaska, the least densely populated state.
Barren Land
Certain areas of the United States have little to no vegetation. A considerable portion of Alaska is covered in tundra, with low-growing vegetation, such as mosses and lichens. Similarly, other regions like Nevada have barren desert landscapes, where few plants grow, due to the hot, dry climate. The vast majority of these areas are located in the western portion of the country. Even Hawaii has a significant amount of barren land due to its volcanic mountains.
Urban Land
About 40% of New Jersey‘s land is considered to be urban. A high percentage of the state has either paved surfaces or buildings. The state is located between two of the largest cities in the United States, Philadelphia and New York, contributing to its high population density. On the other end of the spectrum, Alaska, Wyoming, and Montana have extremely little urban land. They are among the most sparsely populated states in the country.
Calculation Method
States are compared by the percentage of land cover they have in common. For example, in Kentucky, forests cover 47% of the land area, while agricultural land covers 50% and urban areas cover 3%. Therefore, Kentucky gets 0.5 points for forests, 0.5 points for agricultural land, and 0 points for urban areas. In Iowa, forests cover only 8% of the land area, while agricultural land covers 90% and urban areas cover 2%. Therefore, Iowa gets 0.1 points for forests, 0.9 points for agricultural land, and 0 points for urban areas. When the land cover of Kentucky and Iowa is compared, they are credited for 0.5 points for agricultural land and 0.1 points for forested land, for a total of 0.6 out of 1 similarity points.
