PENGARUH PERUBAHAN LANSKAP TERHADAP KINERJA JASA EKOSISTEM HASIL AIR DI SUB DAS OPAK HULU

Khansa Hanun Afifah, Dr. Ir. Hero Marhaento, S.Hut., M.Si., IPM.

2025 | Tesis | S2 Ilmu Kehutanan

INTISARI

Wilayah Sub DAS Opak Hulu mengalami tekanan ekologis berupa perubahan tutupan lahan yang signifikan selama tiga dekade terakhir akibat aktivitas antropogenik dan pengaruh erupsi Gunung Merapi. Dinamika tutupan lahan mendorong perubahan karakteristik lanskap sehingga memengaruhi konektivitas hidrologis dan kondisi aliran di Sub-DAS Opak Hulu. Penelitian ini bertujuan untuk menguantifikasi perubahan karakteristik lanskap berupa komposisi dan konfigurasi lanskap, menguantifikasi perubahan kinerja jasa ekosistem hasil air tahunan (Annual Water Yield/AWY), dan memodelkan pengaruh karakteristik lanskap terhadap hasil air secara temporal pada 1990-2024.

Metode pengambilan data simulasi dilakukan dengan penentuan nilai metrik lanskap dari hasil klasifikasi tutupan lahan dan nilai hasil air tahunan. Klasifikasi tutupan lahan diperoleh dari citra landsat 5, 7, dan 8 melalui Google Earth Engine selama 12 tahun analisis yaitu 1990, 1993, 1996, 2000, 2003, 2007, 2009, 2013, 2015, 2017, 2020, dan 2024. Data perubahan karakteristik lanskap diperoleh dari analisis FRAGSTAT dengan total 10 metrik tingkat lanskap dan kelas. Data perubahan hasil air diperoleh dengan AWY model InVEST. Penentuan model untuk menganalisis pengaruh karakteristik lanskap terhadap kinerja jasa ekosistem hasil air dilakukan dengan uji stepwise regression melalui R-studio.

Hasil penelitian menunjukkan bahwa selama periode 1990–2024 lanskap Sub DAS Opak Hulu mengalami fragmentasi akibat pengelolaan tidak terarah, ditunjukkan dengan peningkatan keragaman tutupan lahan, kompleksitas bentuk patch, penurunan dominasi hutan, dan berkurangnya konektivitas lanskap. Ekspansi lahan terbangun melalui konversi hutan dan lahan pertanian menjadi pendorong utama perubahan pada tingkat kelas. Lahan terbangun berkembang menjadi blok padat dan homogen yang terisolasi, sementara semak belukar dan lahan terbuka menunjukkan pola ketercampuran tinggi dengan tutupan lahan lain. Perubahan total AWY pada 1990-2024 di Sub DAS Opak Hulu mengalami peningkatan hingga 21%. Berdasarkan hasil analisis regresi linear berganda, variabel prediktor seperti komposisi lanskap yakni persentase hutan dan keberagaraman lanskap serta konfigurasi lanskap berupa keterhubungan lanskap, percampuran lahan agrikultur, dan kompleksitas bentuk pada lahan terbuka dan semak belukar berpengaruh signifikan terhadap kinerja ekosistem hasil air AWY dengan model mampu menjelaskan variasi AWY sejumlah 87,08% pada tingkat lanskap dan 97,06% pada tingkat kelas. Temuan ini menegaskan pentingnya mempertimbangkan karakteristik lanskap dalam pengelolaan DAS dan perencanaan konservasi berbasis jasa ekosistem air di wilayah tropis.

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ABSTRACT

The Upper Opak Sub-Watershed has experienced significant ecological pressure due to land cover change over the past three decades, driven by anthropogenic activities and the impact of Mount Merapi's eruptions. These land cover dynamics have altered landscape characteristics, influencing hydrological connectivity and flow conditions within the sub-watershed. This study aimed to (1) quantify changes in landscape composition and configuration, (2) assess changes in annual water yield (AWY), and (3) model the temporal influence of landscape characteristics on water yield from 1990 to 2024.

Data were simulated by calculating landscape metrics derived from classified imagery and annual water yield values. Land cover classification was performed using Landsat 5, 7, and 8 imagery from Google Earth Engine for 12 analysis years: 1990, 1993, 1996, 2000, 2003, 2007, 2009, 2013, 2015, 2017, 2020, and 2024. Changes in landscape characteristics were analyzed using FRAGSTATS, incorporating 10 metrics at both landscape and class levels. Changes in water yield were estimated using the Annual Water Yield model in InVEST. The influence of landscape characteristics on water yield was modeled using stepwise regression analysis in RStudio.

The results indicate that between 1990 and 2024, the landscape of the Upper Opak Sub-Watershed underwent fragmentation due to unmanaged land use, reflected in increased land cover diversity, patch shape complexity, reduced forest dominance, and decreased landscape connectivity. Expansion of built-up areas through the conversion of forests and agricultural lands was the primary driver of change at the class level, resulting in area loss and fragmentation of these land classes. Built-up areas formed dense, homogeneous, and isolated blocks, while shrubland and open land exhibited high mixing with other land cover types. The total AWY increased by 21% from 1990 to 2024. Based on multiple linear regression analysis, significant predictors of AWY included landscape composition metrics (e.g., percent forest cover and landscape diversity) and configuration metrics (e.g., landscape connectivity, agricultural land mixing, and shape complexity of open and shrublands). The regression models explained 87.08% of AWY variation at the landscape level and 97.06% at the class level. These findings underscore the importance of integrating landscape characteristics into watershed management and water ecosystem service-based conservation planning in tropical regions.

 

Kata Kunci : Land Cover, Landscape Characteristics, Annual Water Yield (AWY), InVEST Model, Upper Opak Sub-Watershed