Editing Environmental determinism (section)

=== Effects of terrain on trade and productivity ===
Historians have also noted population densities seem to concentrate on coastlines and that states with large coasts benefit from higher average incomes compared to those in landlocked countries. Coastal living has proven advantageous for centuries as civilizations relied on the coastline and waterways for trade, irrigation, and as a food source.<ref name="Geography and Economic Development" /> Conversely, countries without coastlines or navigable waterways are often less urbanized and have less growth potential due to the slow movement of knowledge capital, technological advances, and people. They also have to rely on costly and time-consuming over-land trade, which usually results in lack of access to regional and international markets, further hindering growth. Additionally, interior locations tend to have both lower population densities and labor-productivity levels. However, factors including fertile soil, nearby rivers, and ecological systems suited for rice or wheat cultivation can give way to dense inland populations.<ref name="Geography and Economic Development" />

[[Nathan Nunn]] and Diego Puga note that though rugged terrain usually makes farming difficult, prevents travel, and limits societal growth, early African states used harsh terrain to their advantage.<ref name="Nunn 20–36">{{cite journal | last1=Nunn | first1=Nathan | last2=Puga | first2=Diego | date=February 2012 | title=Ruggedness: The blessing of bad geography in Africa | url=http://dpuga.economics.utoronto.ca/research/rugged.pdf | journal=The Review of Economics and Statistics | volume=94 | pages=20–36 | doi=10.1162/rest_a_00161 | s2cid=16512034}}</ref> The authors used a terrain ruggedness index to quantify topographic heterogeneity across several regions of Africa, while simultaneously controlling for variables such as diamond availability and soil fertility. The results suggest that historically, ruggedness is strongly correlated with decreased income levels across the globe and has negatively impacted state growth over time. They note that harsh terrain limited the flow of trade goods and decreased crop availability, while isolating communities from developing knowledge capital. However, the study also demonstrated that the terrain had positive effects on some African communities by protecting them from the slave trade. Communities that were located in areas with rugged features could successfully hide from slave traders and protect their homes from being destroyed. The study found that in these areas rugged topography produced long-term economic benefits and aided post-colonial state formation.<ref name="Nunn 20–36" />