Grapes can be grown, over a wide range of latitudes, in climates ranging from very hot (southern California, inland Australia) to very cool (England, Luxembourg, Denmark). Viticulture is practised in very wet climates (parts of England and New Zealand) to very dry ones (Atacama in Chile, Central Valley in California). The topography can be very steep, as in the Mosel valley of Germany or the Douro of Portugal, or very flat plains, as in many regions of Australia and Argentina. vine density can vary enormously: from vineyards planted with large numbers of very small vines, as is common in Champagne and Bordeaux (10,000 vines per ha (4,050 per acre)), to few, large vines as in the Vinho Verde vineyards of Portugal (600 vines per ha). Some vineyards may be tended entirely by manual labour, while others are mechanized. Vineyards may rely on irrigation for their survival where they are grown in deserts, while in others, such as parts of France, irrigation is severely restricted.