The starting line of deep decline

Between the 2011 and 2021 Censuses, published by the National Statistics Institute, the border municipality of Barrancos suffered a demographic drop of 21.6%, establishing itself as the largest proportional loss recorded across the entire national territory during that decade. For those living in the town, this contraction translates into the gradual closure of proximity services, the desertification of streets, and an increasingly narrow economic base to sustain the population remaining in the territory.

At the district level, definitive data released by the National Statistics Institute in 2021 show that the resident population in the district of Beja stood at 144,401 people, reflecting an overall decrease of 5.5% compared to 2011. This demographic erosion does not only affect large urban agglomerations, but corrodes the social fabric of entire parishes, where the proportion between active generations and the elderly reaches levels of financial and care unsustainability.

Broadening the regional field of vision, statistical reports published by the Fundação Francisco Manuel dos Santos via Pordata in July 2025 indicate that Alto Alentejo recorded the largest year-on-year population reduction in the country, settling at a negative variation of -0.49%. In direct comparison with the national average, which benefited from a global migratory impulse to reach a resident population of 11,424,031 inhabitants in 2025, according to revised data from the National Statistics Institute, the Alentejo interior deepens its demographic isolation.

The gap between the dynamic coastline and the aged interior

The Alentejo geography is far from presenting a homogeneous portrait, dividing itself between sub-regions with completely opposite dynamics. According to Pordata statistical data from 2025, while Alto Alentejo leads the losses, Baixo Alentejo and Alentejo Central recorded more moderate decreases of -0.07% and -0.03%, respectively. At the opposite pole, the Pordata report from July 2025 showed that Alentejo Litoral bucked the regional trend by registering a positive population growth of 0.82%.

This coastal dynamism and that of certain interior areas finds a direct reflection in specific municipalities that escape the general rule of desertification. According to the 2021 Census from the National Statistics Institute, the municipality of Odemira bucked the generalized drop in the district of Beja by growing 13.3%. In the same vein, Pordata data for 2025 show that interior municipalities such as Arraiolos and Alter do Chão recorded population increases of 1.36% and 1.32%, respectively.

For those who inhabit these counter-cyclical municipalities, daily reality differs drastically from that experienced a few kilometers away. In Odemira or Arraiolos, the arrival of new residents alters the dynamics of the housing market and local schools, while in municipalities like Gavião the scenario is the opposite, with the municipality reaching an extreme aging index of 535.1 elderly people per 100 young people in 2025, according to Pordata records.

The fallacy of absolute decline and the weight of immigration

The most obvious reading would point to an absolute, uniform, and irreversible demographic decline across the entire Alentejo territory, driven by decades of negative natural balances and accelerated aging. However, this premise falls apart when recent migratory flows and the economic attraction capacity of specific poles are analyzed. The national migratory balance, which led the resident population in Portugal to reach 11,424,031 inhabitants in 2025 according to the National Statistics Institute, has direct reflections in agricultural and industrial territories of Alentejo.

Proof that decline is not universal lies in the contrast between the deep interior and areas of intensive agriculture or attractive urban proximity. While the demographic sustainability index in Barrancos stood at just 2.84 in 2025, and in municipalities like Nisa dropped to 1.36 and Mértola to 1.51 — values well below the national average of 2.59 reported by Pordata in 2025 — municipalities with large-scale agricultural projects or new residential dynamics temporarily stabilize their population base with external flows.

Despite these occasional exceptions, the underlying age structure continues to strongly pressure the region as a whole. According to National Statistics Institute projections from 2025, the number of young people in Alentejo will drop from 57,638 individuals recorded in 2024 to just 41,009 by the horizon of 2100. Over the same period, the regional aging index will skyrocket from 227 elderly people per 100 young people counted in 2024 to 302 at the end of the century, showing that structural demographic pressure remains unchanged in the long term.

The pressure of extreme aging on local communities

Demographic aging in Alentejo far surpasses the national average, placing the region in a position of evident comparative vulnerability. According to Pordata data for 2026, Portugal already ranks as the third country in the European Union with the highest aging index, presenting a national ratio of 182 elderly people per 100 young people. In the Alentejo context, this ratio is largely surpassed, with the region having been pointed out in an OECD case study published in 2021 as holding one of the fastest demographic decreases and the highest aging rate among the organization's large regions.

This reality carries an unwieldy weight on the working-age population that remains in the 47 Alentejo municipalities. According to the National Statistics Institute Highlight published in September 2025 on demographic projections, the elderly dependency ratio in Portugal will move from 39 elderly people per 100 working-age people in 2024 to 73 in 2100. For those living in the interior of Alentejo, this translates into a chronic shortage of caregivers, increased pressure on local health centers, and the need for deep restructuring of social equipment.

Given the scale of this social pressure, the Assembly of the Republic approved Law no. 7/2026, of February 25, formalizing the Statute of the Elderly Person, with the objective framed by Pordata of mitigating impacts in the regions most affected by aging. For an ordinary citizen residing in a municipality like Gavião or Mértola, the effectiveness of these legal measures is measured by the practical capacity to maintain active social responses in a territory where the age pyramid is totally inverted.

What remains for the future of the 47 municipalities

The future sustainability of Alentejo municipalities is played out in their capacity to attract and retain new generations and migratory flows, countering the gap that separates the dynamic coastline from the desertified rural interior. Official numbers show that the decline does not affect all municipalities with the same intensity, with pockets of growth existing driven by local economic dynamics and new currents of foreign and national settlement.

However, for the general population of the 47 municipalities of Alentejo, the horizon of 2100 is drawn with less than three-quarters of the current young people and a regional aging index projected by the National Statistics Institute to reach 302 elderly people per 100 young people. The practical challenge for those who lead and inhabit these territories lies in the daily management of municipalities where the loss of half the population in some parishes is already a consummated reality or an imminent risk.

The application of legal instruments such as the 2026 Elderly Person Statute and the constant monitoring of Pordata and National Statistics Institute indicators will allow for an evaluation, year by year, of whether public policies can halt social rupture or if the Alentejo interior will continue to witness the progressive loss of its demographic base.