Analysis of Annual Nighttime Light Changes

This analysis focuses on the annual nighttime light (NTL) maps of three islands: Madeira, Graciosa, and Gran Canarias, for the years 2012, 2016, 2020 and 2023. These maps provide insights into the patterns of artificial light intensity across the islands, reflecting trends in urbanization, infrastructure development, and human activity. By examining changes in light levels over time, we can observe how different regions have experienced growth, stability, or decline in artificial lighting, offering a window into the socioeconomic and environmental dynamics of each island.

These maps illustrate the distribution and intensity of nighttime light (NTL) across the islands, using a color gradient from lowest (gray) to highest (red) light levels. The overall trends for each island are analyzed, highlighting key changes during this period to offer a clear interpretation of the results and potential factors influencing these shifts.

The maps display a slow reduction in man-made illumination along the coastline of Madeira throughout the years. Between 2012 and 2023, there has been a gradual decrease in the intensity of high and medium light levels (red and orange) in the southeastern and southwestern areas of the island.

In the southeast area, especially in Funchal, the brightness remains consistently at its highest level. The area remains the epicenter of abundant artificial light and the relentless growth of cities. The increase in dim and moderate lighting has become more noticeable in this region, reflecting the urban development and the possible growth of tourism, residential areas, and commercial establishments along the coast, where population densities are typically higher. Over time, the green and pale yellow patches of dim and extremely dim light have grown, indicating a slow spread of sparse urban zones or heightened rural illumination. This tendency indicates a gradual expansion of human settlements or buildings into sparsely populated regions, with the possibility of increased rural development from 2016 to 2023. This growth may also indicate the emergence of roads, amenities, or public services that illuminate once shadowy places. Nevertheless, the brightness in these zones remains modest, suggesting a sparser population or less advanced development in contrast to the coastal areas.

The gray regions of the island's mountainous interior have been mostly unaffected by artificial light, suggesting a sense of permanence in the island's untouched rural landscapes. It is probable that these shadowy areas form a component of nature reserves or rough landscapes that are not very suitable for construction, thus safeguarding the original nocturnal surroundings.

The soft yellow light on Graciosa is scarce and concentrated, mainly found in the northeastern and central areas of the island. In contrast to highly developed regions, the island keeps a predominantly subtle artificial light presence year-round, with limited growth in brighter lighting. The light presence in the northeastern area stands out consistently, possibly indicating the primary residential areas or important infrastructure centers of Graciosa.

Between 2012 and 2023, Graciosa underwent a continuous growth of extremely dim illumination (green zones), mainly in its central and southern areas. The slow rise indicates a small amount of progress, possibly because of the introduction of electricity in rural areas or minor upgrades to infrastructure, with the general brightness of artificial light staying at a low level.

In 2016, there is a slight increase in medium-intensity light (orange) around the northeast, marking a period of increased urban or infrastructural development. This uptick could reflect the growth of public facilities or commercial activity. However, this medium-intensity light appears to be temporary, as it does not persist in the subsequent years (2020 and 2023), suggesting that this might have been a short-lived or localized phenomenon.

From 2012 to 2023, the eastern coast of Gran Canarias, particularly near the northeast, shows consistently high-intensity light (red), likely representing the main urban centers such as Las Palmas de Gran Canaria. This area remains the brightest across all years, reflecting persistent urban activity. The southern region, known for tourism (e.g., Maspalomas), also maintains a significant level of light, mostly in the medium-to-high-intensity range (orange and red).

Very low (green) and low-intensity light (yellow) areas show a gradual expansion across the island’s interior and western regions, where previously dark zones (gray) become illuminated. This trend is noticeable in the interior and northern areas between 2012 and 2020, where urbanization or infrastructure development might be causing an increase in artificial lighting.

The 2016 map shows a notable increase in high-intensity lighting along the eastern and southern coastal areas compared to 2012, suggesting growth in urban and commercial activities. However, some of this intensity decreases by 2020 and 2023, indicating a possible stabilization or reduction of light usage in these areas.

From 2020 to 2023, while the general lighting pattern remains similar, the high-intensity areas seem to slightly decrease, especially in the interior and western parts of the island. This may be due to energy-saving policies, reduced tourism activity, or efforts to manage light pollution. The overall intensity remains stable but with a focus on reducing light spread, as indicated by the reduction of medium and high-intensity zones in 2023 compared to 2016.