Living Land

[

] 60

Aridity index for the Mediterranean region, 1950-2000

Source: Lúcio do Rosário, based on FAO (PM) CGIAR-CSI

ized by the occurrence of below-normal precipitation values,

recorded during an extended period, associated with a change

in the distribution of rainfall, with significant reduction of

precipitation in spring and an increasing period of water

deficit. This affects the normal development of vegetation and

weakens soil resources and agricultural production.

However, other major causes of desertification can be seen

in all the unsustainable activities linked to the use of natural

resources and agriculture, including agricultural bad practices.

These include deep and continuous crop farming on greater

slopes; monoculture that leads to loss of soil nutrients and its

breakdown; the use of species not suited to the climate or soil;

contamination of soil by overuse of fertilizers, herbicides and

pesticides; use of heavy farmmachinery, and use of poor-quality

water with the consequent risk of soil salinization and sodization.

Activities related to livestock may also cause severe soil/water

degradation, such as grazing or excessive livestock density in

a given area resulting in the appearance of tracks favouring

shallow seepage and soil compaction by excessive cattle tram-

pling. We should also mention the extensive destruction of

shrubland for land use changes, deforestation and the exces-

sive consumption of water (tourism and agriculture irrigation)

that lead to the reduction and depletion of groundwater, which

often contains excess salts and causes soil salinization. Last but

not least, soil sealing by the creation of infrastructures, equip-

ment and urbanization also have an effect.

One of the main goals of NAPCD 2014 was to develop

cartography and indicators to help decision makers find

appropriate solutions to the management of resources in the

dry territories and at the same time favour and encourage the

recovery of degraded lands areas.

Considering the cartography of the aridity index (the ratio

between precipitation and potential evapotranspiration) for

Portugal it is clear that the area susceptible to desertification

has increased in the last half-century. This is most evident

when comparing the periods of 1970-2000 and 1980-2010,

and even more relevant when looking only at the decade 2000-

2010, which had some particularly severe annual droughts.

Therefore, the aridity or the equivalent susceptibility to

desertification have affected 58 per cent of the territory of conti-

nental Portugal in the last three decades (1980-2010), while in

1960-1990, 36 per cent was affected. In this context the areas

of the south, central and northern interior were included, but

it should be noted that at a national level it is also necessary to

consider the arid areas of south-eastern Madeira Island and the

islands of Porto Santo, Desertas and Selvagens.

The indicator of land productivity relates to the services

provided by the ecosystem and includes information about the

Semi-arid

Dry subhumid

Arid

Wet

Moist subhumid

Very arid

iving

and