The highest, wildest areas lie within the Peneda-Geres national park, and during a walking tour last week I found myself comparing the conservation problems of Portugal with those nearer home. The climate of the Alto Minho is gentler than that of Scotland: rainfall is high, but frost and snow are rare. Yet the environment is even harsher, and seems to support far fewer birds and animals.
Bears are said to have died out in 1650, and wild goats in 1890; but boar and roe deer are fairly numerous, and a few wolves still prowl the heights. Within the national park these last are protected; but gun licences are easy to obtain, and farmers living at the sanctuary's edges blast off at any four-legged predator they set eyes on. Of course we longed to see one, but had to be content with a set of three half-inch tracks printed in a patch of mud.
We did see wild ponies, in herds of 10 or a dozen, each with a fiery little stallion in charge. Almost all the mares had foals at foot - a fact that seemed to refute one farmer's claim that wolves prey heavily on the horses' offspring.
As for birds, cuckoos called frequently at the fringes of the park, and we heard a nightingale singing in a thicket of young oaks. Yet in three long days' walking we spotted nothing in the sky over the high ground except two golden eagles and a hen-harrier. Lower down, a single pair of partridges was the only sign of game.
On any comparable transit of the Highlands we would have seen eagles, grouse, ptarmigan, hooded crows, ravens and large numbers of red deer. Between the tumbled piles of granite, the heather was of poor quality: huge areas had been invaded by gorse and bracken, and there was practically nothing for herbivores to eat. Attempts had been made to encourage new growth by setting fire to the gorse - indeed, the number of blackened patches was astonishing.
Our guide explained that a burnt-out area is officially deemed to have become less valuable, and that permission can be obtained to build a house on it, even within the park's boundaries. Outside, many blazes are apparently started for fun: anything to liven up a dull Saturday night and watch the fire brigade turn out.
Like Scotland, Portugal has no law of trespass. Provided you do not cause damage, you can walk anywhere you like. Down in the farmland we followed paths that twisted between terraced fields and vineyards; in the mountains we pounded the old pilgrim trails leading to and from the great shrine at Peneda.
These centuries-old tracks are works of art in themselves, the product of incredible human effort. They reminded me of the pony paths built by Victorian landlords to gain access to remote parts of their Highland estates, but they are on an altogether grander scale, being shod with granite boulders, some weighing a few pounds, some many hundredweight.
Beside the tracks march walls made of granite slabs set vertically on edge, with the gaps between neatly filled by smaller stones. So we walked with rock beneath our boots, rock to right and left, and rock towering above us in gigantic cliffs and outcrops.
One final similarity with Scotland: the weather was all to blazes. "Here it never rains after mid-May," someone told us - but boy, was he wrong! Every afternoon clouds massed, lightning snaked down, thunder cannonaded round the peaks, and phenomenal deluges set the granite gleaming. The result was that we usually reached base sodden, more convinced than ever that global warming is here to stay.