## 3 Results
### Estimation of Gross Primary Productivity (GPP)  
GPP is a key indicator of photosynthetic activity within an ecosystem [22], signifying the amount of carbon dioxide captured by plants and its conversion into organic compounds. In our study area, where the economy and food security are intricately linked to agricultural productivity, understanding GPP is critical [24]. It provides insights into the health of vegetation and its response to climatic changes, which are essential for maintaining food security stability systems [25]. For the climatic changes impacting the study area, the GPP data presented in Figure 8 and Table 7 offer an important perspective on the region's ecological productivity. The data, categorized by classes likely indicative of varying vegetation cover or land use types, reveal the amount of carbon assimilation that occurred for the years 2005, 2010, 2015, and 2020. The absence of data for Class 1 point to areas beyond the reach of vegetative cover or regions where data collection was not feasible. However, regarding Class 2, which falls under 3795 g C m\({}^{-2}\) yr\({}^{-1}\), the GPP figures suggest a gradation in productivity. In 2005, the total GPP of the study area for Class 2 amounted to 2,471,700 g yr\({}^{-1}\), while for Class 3 (8764 g C m\({}^{-2}\) yr\({}^{-1}\)), it was 2,931,420 g yr\({}^{-1}\), and for Class 4 (12,985 g C m\({}^{-2}\) yr\({}^{-1}\)), it was 2,931,000 g yr\({}^{-1}\). Classes 2 and 3 primarily cover the crop area, while Class 4 encompasses the forest or higher vegetation areas. By applying Equation 4, the pattern appears to remain relatively steady over the following years, indicating a level of consistency in productivity. However, in 2010, GPP decreased by \(-\)570 g yr\({}^{-1}\) compared to other years. This drop can be attributed to the increase in temperature by 1 \({}^{\circ}\)C in 2010 (Figure 9). It is estimated that the GPP loss will amount to \(-\)2500 g yr\({}^{-1}\) by 2100, assuming a 3 \({}^{\circ}\)C rise in temperature.  
These values also represent the carbon uptake by the vegetation, which has direct implications for agricultural output and the broader ecosystem services. Understanding the trends in these values over time is vital as they reflect the region's ability to sustain crop production amidst environmental and climatic challenges. Increasing GPP values signal healthier, more productive vegetation, potentially benefiting food security. Conversely, declining values might point to ecological stress, emphasizing the need for adaptive strategies to ensure continued agricultural viability. In this context, GPP estimation served as an indicator of ecological function and as a gauge for the sustainability of the region's food production systems in the face of climatic variability. This highlights the importance of proactive management and policymaking aimed at enhancing the resilience of agricultural systems, preserving ecological balance, and supporting the food security of the study area in the period of changing climate patterns.  
Figure 8: Comparative GPP trends across various years depicting vegetative productivity the study area: (**A**) 2005, (**B**) 2010, (**C**) 2015, and (**D**) 2020.