Where are older dunes held in place by vegetation found?

Older dunes held in place by vegetation are found in many regions that are now subhumid or humid, serving as evidence that these areas were once more arid than they are today.1

Examples of these stabilized landscapes include:

• North American High Plains: Specifically the Sand Hills region of north-central Nebraska and southern South Dakota, where dunes formed thousands of years ago are now covered by rich grassland.12
• Hungary and Mongolia: These regions also feature fixed sands covered by rich grassland.1
• Poland: In this region, older fixed dunes are typically covered with coniferous forests.1

These stabilized dunes often retain rounded and subdued forms that resemble those found in active sand seas. Their existence indicates that the conditions of low rainfall necessary for the formation of true dunes once extended far beyond the margins of modern arid regions.13