Despite influences from the humid Atlantic and the continental meseta, a Mediterranean type of climate predominates Portugal. Cool, rainy winters contrast with hot, dry summers, summer heat and drought being greater in the south. There is a marked rain-shadow effect in the north, where the windward mountain slopes receive 100 inches of rain annually, while the eastern Tnis-os-Montes receive only 20 inches. All Portugal south of the Tagus River receives less than 32 inches, and less than 16 inches falls in the eastern Algarve. Winds are generally westerly and sea fogs are common along the Minho coast. The 15°C mean annual isotherm crosses the country along the line of the Tagus. More important, however, is the contrast between the coast and the interior. Winter temperatures are around l2°C along the coast (though warmer in the south) and around 7°C inland. Summer temperatures average 28°C on the coast and 17°C inland.
Vegetation and Wildlife
Plant and animal life is very similar to that of Spain, except that the humid climate of northern Portugal makes that region the most densely-forested in the Iberian Peninsula. Because climatic elements from the Atlantic and the Mediterranean intermingle, plants from northern Europe flourish side by side with semitropical varieties from the Mediterranean, Africa and South America, making Portugal a botanist's paradise. But there are latitudinal contrasts in the distribution of species. North of the Mondego River 57% of the plants are European species and 26% Mediterranean; between the Mondego and the Tagus the proportions become 38% and 42% respectively, and south of the Tagus 29% and 46%. The Algarve, with its fig, carob and almond trees, is especially distinctive.
Though there has been some industrial development, Portugal remains a largely agricultural country. The north is characterized by small, intensively-cultivated family farms, many of less than 5 ha, and some fragmented. In the south (except the Algarve), large farms of more than 100 ha are usual. Before the 1974 revolution, about 70% of all farms were owner-operated, 25% were rented, and the rest were either worked by sharecroppers or in association with the large farms. In 1974-75 much land was expropriated and given to the peasants or organized into cooperatives. More moderate land reform is continuing.
The economy of the middle Douro valley, a district stretching 60 miles from the Spanish border to within 50 miles of Porto, is entirely geared to a single product-port wine. Flights of terraces, the accumulated achievement of generations, may rise uninterrupted for 1,000 feet from the river's edge to the rounded plateaus of the Tnis-os-Montes.
Britain assured port of a guaranteed market (in return for English textiles) by the Methuen Treaty (1703). The Douro district received legal protection; only wine from this district could bear the name "port". The UK still buys most of the output.
Changing social habits, especially the popularity of sherry, have caused a decline in consumption, however, so many of the Douro terraces have now been replanted with olives.
Wine was made in Portugal at the time of the ancient Greeks, and the vine is now widely cultivated, other wines than port also being exported.
Only rarely is the vine a monoculture, however, except in recently planted areas such as the Estremadura Ribatejo lowlands around Cartaxo. About 75% of the total cultivated land is devoted to arable farming. Beans, potatoes and the poorer cereals (rye, oats and corn) are grown in the north; wheat is grown on the vast treeless fields (the campos) of the large estates of Alentejo.
About 400 000 ha, mainly in the drier regions, are devoted to olives.
The basic contrast between northern, humid, Atlantic Portugal and the more Mediterranean south is reflected in livestock distribution. Cattle predominate in the north, especially in Minho, and sheep and goats in the south. Hogs are ubiquitous.
Animal power-oxen and mules for transportation-still dominates Portuguese agriculture, though some mechanization has been introduced, especially on the broad, flatter farmlands of Alentejo.