Long-Term Monitoring of Arundo donax L. Range in Albufera Wetland (Spain): Management Challenges and Policy Implications

Arundo donax L. (common reed), a highly invasive species in Mediterranean wetlands such as the Albufera Natural Park, poses significant ecological and management challenges. Using Landsat-5 and Sentinel-2 NDVI data, this study quantified changes in its coverage between 1996 and 2024. The results reveal a significant expansion, showing a decreasing trend (91.4 ha in 1996 to 62.5 ha in 2011; −31.6%) followed by a clear rebound (83.5 ha in 2024; +33.6%), especially in the southern shrublands of the lagoon. A Mann–Kendall analysis confirmed a significant decreasing trend during 1996–2011 and an increasing trend during 2011–2024 (p < 0.05). The results indicate that previous control efforts reduced A. donax cover but that the species has recolonised after 2011, likely due to discontinuous management. These dynamics emphasise that long-term monitoring is required. Management strategies must focus on targeting the rhizome and implementing long-term monitoring programmes spanning three to five years. The utilisation of remote sensing methodologies proved effective in the monitoring of coverage, thereby facilitating the development of remediation strategies. It is imperative that actions accord primacy to critical areas such as the south and canals, complemented by native restoration and enhanced inter-administrative coordination, with the communication of benefits such as flood risk reduction. A balanced approach is required that considers ecological objectives, risks, and socio-political aspects.