4.1. Mean Annual temperature trend
This Fig. 2 illustrates the spatial distribution of annual mean temperature trends across the Algerian steppe for the period 1951–2022, as calculated using Sen’s slope method. The results show a generalized warming trend across the entire region, with a notable spatial gradient. The strongest warming signals are observed in the central and northeastern parts of the steppe, particularly in the wilayas of Djelfa, Laghouat, and Tébessa, where the Sen’s slope values reach 0.028°C/year in some areas.
Conversely, lower but still positive trends are detected in the southwestern and western steppe, notably within the Naâma, El Bayadh, and Saïda regions. Although these areas exhibit less intense warming compared to the northeastern steppe, the consistent positive trends throughout the map confirm that no part of the steppe has been exempt from warming over the last seven decades.
4.2. Annual Precipitation Trend
Figure 3 displays the spatial distribution of annual precipitation trends across the Algerian steppe between 1951 and 2022, based on Sen’s slope estimates. The trends range from − 2.285 mm/year (low) to − 0.098 mm/year (high), indicating an overall tendency toward decreasing rainfall. Notably, this classification uses an inverted logic, in which smaller (less negative) but statistically significant changes are considered more alarming (High), as they correspond to consistent and detectable decreases, while larger fluctuations with no statistical significance are classified as Low.
The northwestern region, notably in the wilayas of Naâma, northern El Bayadh, and Saïda, is characterized by low Sen’s slope values, corresponding to small but statistically significant decreases in annual precipitation. These trends, although limited in magnitude, are consistent and persistent over the study period.
In contrast, the southern and eastern steppe zones, including Laghouat, Djelfa, and Tébessa, exhibit high Sen’s slope values, indicating larger decreases in precipitation. However, these trends are not statistically significant, due to strong interannual variability, and thus do not reflect a stable long-term shift.
This spatial distribution reveals a distinct contrast: areas with modest but consistent reductions in rainfall are mainly located in the northwest, while more erratic and variable declines occur in the south and east.
4.3. Temperature Trend Classes
The map in Fig. 4 depicts how annual temperature trends across the Algerian steppe have been distributed into three categories—low, moderate, and high—based on Sen’s slope values between 1951 and 2022. The classification was derived using the 25th and 75th percentiles to delimit the intensity thresholds.
A large portion of the steppe falls under the low trend class, indicating relatively modest increases in annual temperature across most of the region. In contrast, a moderate trend is only detected in a confined zone within central Laghouat, suggesting an intermediate rate of warming in that area.
Areas assigned to the high trend category are mainly located in the southwestern part of Naâma and a broad belt within the eastern steppe, including southern Djelfa, M’Sila, Biskra, Batna, Khenchela, and Tébessa. These regions exhibit the most pronounced warming signals recorded in the dataset.
The resulting distribution points to clear regional disparities in the pace of temperature change across the steppe.
4.4. Precipitation Trend Classes
Figure 5 shows the spatial categorization of precipitation trends across the Algerian steppe, calculated using Sen’s slope over the 1951–2022 period. Unlike temperature, precipitation trends were interpreted using an inverse logic: the stronger the negative slope, the greater the potential climatic risk.
The most pronounced decreases in annual precipitation appear in the southern parts of Tlemcen and Sidi Bel Abbès, as well as the northern sector of Naâma, all of which fall into the high decrease category.
Regions classified as moderate decrease extend over a wide corridor spanning the southern areas of Naâma and El Bayadh, as well as portions of Laghouat, the southeast of Djelfa, southern M’Sila, Biskra, Batna, and the western part of Khenchela.
In contrast, the remaining steppe areas show comparatively smaller declines in precipitation over time and are therefore categorized within the low decrease group.
This classification delineates zones where rainfall reduction has been more sustained or marked over the study period.
4.5. Climate Risk Levels
Figure 6. Spatial distribution of climate risk levels across the Algerian steppe (1951–2022), based on the combined classification of temperature and precipitation trends using a 3×3 matrix. The resulting categories range from very low to very high risk, following the IPCC's conceptual framework. This map highlights areas where overlapping climate trends contribute to differentiated levels of exposure and potential vulnerability.
Figure 6 presents the spatial distribution of aggregated climate risk levels across the Algerian steppe, derived from the combined classification of temperature and precipitation trends. The integration of these two variables, structured through a 3×3 matrix, results in five levels of risk—ranging from very low to very high—according to the IPCC’s framework for compound climate impacts.
The very high-risk category is limited to a few steppe areas, particularly within Biskra, Batna, and the western part of Khenchela, where the convergence of strong warming and consistent rainfall decrease is most notable.
A high-risk level is also evident across several zones, including the southern parts of Naâma and El Bayadh, as well as Djelfa and Tébessa, which show notable trends for both climatic variables.
In contrast, a low-risk zone emerges in the northern section of the western steppe, extending eastward to include the northern part of Djelfa, where both temperature and precipitation changes remain limited.
The moderate risk level, representing intermediate combinations of temperature and rainfall trends, occupies the majority of the steppe landscape.
This spatial distribution of risk reflects the interplay between warming intensity and rainfall reduction across different ecological zones within the Algerian steppe.