Geography has long influenced the economy of the Ukrainian lands. Rich fertile soils (such as chernozem areas) made the area a "breadbasket": for ancient Greece as well as for early modern Europe. The maintenance of trade corridors – the route from the Varangians to the Greeks and access through the Straits to the Mediterranean world – became important. Mineral resources encouraged industrialisation – notably in the Donbas – from the 19th century onwards. But the lack of secure borders meant repeated interruptions in economic development. Steppe nomads and other conquerors - Cumans, Mongols, Tatars for example, sometimes saw plundering as more important than fostering economic development. In the 16th to 18th centuries, the wastelands of the Wild Fields left much of Ukraine as an area of tentatively militarised outposts prior to tsarist Russia's extension of its power into the region in the 17th and 18th centuries.