Penjelasan Data Kehilangan Tutupan Hutan Tahunan

Setiap tahun, kami menganalisis data tahunan mengenai kehilangan tutupan hutan untuk menghasilkan wawasan tentang kondisi hutan dunia. Anda dapat membaca informasi terbaru mengenai hutan dunia di Forest Pulse, dan menjelajahi temuan lebih lanjut melalui indikator-indikator Global Forest Review (GFR). Namun, apa yang diukur oleh data ini dan bagaimana perbandingannya dengan perkiraan deforestasi resmi lainnya? Berikut adalah hal-hal yang perlu Anda ketahui mengenai data ini.

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Apa itu kehilangan tutupan pohon?

Data kehilangan tutupan pohon  mencatat gangguan terhadap tutupan pohon, yang didefinisikan sebagai vegetasi berkayu dengan ketinggian setidaknya 5 meter — pelajari lebih lanjut tentang tutupan pohon di Istilah dan Definisi Utama Istilah dan Definisi Utama .

Kehilangan tutupan pohon mencakup gangguan yang menghilangkan setidaknya setengah dari tutupan pohon dalam piksel berukuran 30 meter, dan dideteksi secara tahunan untuk setiap tahun kalender. Hanya tahun pertama kehilangan yang terjadi setelah tahun 2000 yang dicatat. Artinya, jika terjadi beberapa gangguan seiring waktu dalam piksel yang sama, hanya peristiwa gangguan pertama yang disertakan.

Gangguan mencakup kematian atau penebangan pohon di hutan alam serta di perkebunan serat kayu atau tanaman hutan, agroforestri, taman kota, atau area lain dengan tutupan pohon. Kehilangan tutupan pohon dapat disebabkan oleh faktor manusia, seperti pembukaan lahan untuk pertanian, penebangan atau pemanenan kayu — yang semuanya dapat bersifat legal atau ilegal — atau akibat peristiwa alam seperti badai, kebakaran hutan, longsor, banjir, atau wabah hama. Kehilangan ini juga dapat bersifat permanen atau sementara, artinya hutan dapat tumbuh kembali atau pulih setelah gangguan.

Data kehilangan tutupan pohon dapat disaring berdasarkan kumpulan data acuan untuk memfokuskan pada kehilangan yang paling mengkhawatirkan, seperti kawasan hutan primer ( lihat di bawah ). 

Apa perbedaan antara kehilangan tutupan pohon dengan deforestasi?

Hilangnya tutupan pohon tidak selalu berarti deforestasi, yang umumnya merujuk pada perubahan permanen yang disebabkan oleh manusia dari hutan menjadi penggunaan lahan lain. Beberapa bentuk hilangnya tutupan pohon yang disebabkan oleh manusia, seperti konversi hutan alam menjadi lahan pertanian, secara luas dianggap sebagai deforestasi, sementara bentuk lain, seperti penebangan kayu di hutan tanaman industri atau gangguan alam, sering kali tidak dianggap demikian — baca lebih lanjut mengenai perbedaannya di bagian Istilah dan Definisi Utama.

Dalam beberapa kasus, seperti pada Deforestation and Restoration Targets Tracker, kami menggunakan proksi untuk deforestasi. Proksi tersebut menggunakan data mengenai faktor pendorong kehilangan tutupan pohon  dan mencakup seluruh kehilangan tutupan pohon secara global akibat pertanian permanen, komoditas keras (infrastruktur tambang atau energi), serta perluasan pemukiman dan infrastruktur, serta kehilangan di hutan primer tropis basah akibat pertanian berpindah. Kehilangan sementara, seperti akibat kebakaran atau aktivitas penebangan, tidak termasuk.

Apa dasar pengukuran yang kami gunakan untuk mengukur kehilangan tutupan pohon?

Statistik kehilangan tutupan pohon di seluruh GFR (kecuali dinyatakan lain), dan di Global Forest Watch, menggunakan acuan awal tutupan pohon dengan kepadatan kanopi lebih dari 30 persen pada tahun 2000. Ini berarti bahwa kehilangan di dalam area dengan kepadatan kanopi 30% ini termasuk, tetapi kehilangan di area dengan kepadatan kanopi lebih rendah atau di area yang telah tumbuh kembali sejak tahun 2000 tidak termasuk.

Dalam Forest Pulse, kami terutama berfokus pada kehilangan hutan primer tropis karena hutan tropis mengalami sebagian besar (94%) deforestasi dunia, dan kehilangan di area tersebut memiliki dampak besar pada keanekaragaman hayati dan penyimpanan karbon. Meskipun kehilangan ini pada akhirnya dapat dibalikkan, akan membutuhkan puluhan tahun bagi habitat dan cadangan karbon tersebut untuk pulih, dan kehilangan keanekaragaman hayati permanen mungkin terjadi.

Untuk analisis ini, kami menggunakan data mengenai luas hutan primer tropis basah pada tahun 2001  sebagai acuan awal. Dalam kumpulan data ini, hutan primer didefinisikan sebagai hutan tropis basah yang matang yang belum sepenuhnya ditebang dan tumbuh kembali dalam sejarah baru-baru ini, dan kehilangan tutupan pohon dalam acuan awal ini tidak mencakup kehilangan di hutan sekunder muda, perkebunan, atau tanaman pohon. 

Apa saja yang termasuk dalam kehilangan tutupan pohon akibat kebakaran?

Kami melaporkan secara khusus mengenai kehilangan tutupan pohon akibat kebakaran karena kebakaran sering kali menjadi salah satu penyebab utama kehilangan tutupan pohon secara global. Data kehilangan tutupan pohon akibat kebakaran  membedakan kehilangan yang disebabkan oleh kebakaran dari semua penyebab kehilangan lainnya untuk setiap piksel kehilangan tutupan pohon berukuran 30 meter dengan menggunakan model pembelajaran mesin untuk mendeteksi pohon yang terbakar.

Data ini mencakup kebakaran hutan alami dan kebakaran yang disengaja yang mengakibatkan hilangnya tutupan pohon secara langsung, termasuk kebakaran tidak terkendali yang dipicu oleh manusia untuk keperluan pertanian, perburuan, rekreasi, atau pembakaran yang disengaja. Namun, kasus di mana pohon-pohon ditebang terlebih dahulu dan sisa vegetasi kemudian dibakar tidak dimasukkan karena penyebab utama hilangnya tutupan pohon adalah penebangan mekanis.

Bagaimana data kehilangan tutupan pohon telah meningkat seiring waktu, dan bagaimana hal ini memengaruhi perbandingan antartahun?

Penyesuaian algoritme dan data satelit yang lebih baik telah meningkatkan kumpulan data kehilangan tutupan pohon dari waktu ke waktu. Algoritme asli dikembangkan untuk tahun 2001-2012 dan menetapkan kehilangan pada satu tahun dalam rentang waktu tersebut. Perbaikan selanjutnya dikembangkan untuk periode waktu berikut:

  • 2013-2014: Model interval pendek, menjumlahkan tahun 2013 dan 2014 dengan menilai perubahan dalam interval 4 tahun.
  • 2015-2017: Data Landsat 8 dimasukkan; algoritme deteksi perubahan tahunan diterapkan menggunakan model yang dikalibrasi secara regional dan lokal.
  • 2018-2022: Data Landsat Analysis Ready Koleksi 2 dimasukkan, serta algoritme deteksi perubahan yang ditingkatkan menggunakan model yang dikalibrasi secara lokal.
  • 2023-2024: Kumpulan data gangguan lahan DIST-ALERT dimasukkan untuk membantu mendeteksi perubahan pada akhir musim.

Secara keseluruhan, peningkatan ini telah menghasilkan sensitivitas yang lebih tinggi dalam mendeteksi perubahan seperti penebangan selektif, pertanian berpindah skala kecil, dan kebakaran. Penambahan DIST-ALERT juga telah meningkatkan deteksi kehilangan pada akhir musim yang sebelumnya terlewatkan hingga tahun berikutnya akibat keterbatasan data satelit atau tutupan awan. Selain perubahan metodologis, variasi ketersediaan citra satelit (yang secara umum meningkat seiring waktu) juga berarti terdapat ketidakkonsistenan dalam kualitas dan jumlah citra yang tersedia untuk mengumpulkan data setiap tahun.

Untuk mengatasi ketidakkonsistenan ini, kami menilai rata-rata bergerak tiga tahun untuk menafsirkan tren jangka panjang, dan juga mengabaikan peningkatan kehilangan pasca-2012 di tempat-tempat yang kemungkinan besar terkena dampak perubahan ini, seperti Afrika Tengah dan Asia tropis.

Bagaimana perbandingan kehilangan tutupan pohon dengan sistem pemantauan lainnya?

Ada perbedaan definisi dan metodologi yang penting antara data kehilangan tutupan pohon yang disajikan dalam GFR dan sistem pemantauan nasional — seperti PRODES di Brasil dan SIMONTANA di Indonesia. Kumpulan data ini memiliki kelebihan dan tujuan yang berbeda. Data tersebut dapat menyajikan informasi pelengkap yang dapat membantu kita lebih memahami berbagai jenis perubahan di dalam hutan, tetapi penting untuk memahami perbedaannya sebelum membandingkannya. Meskipun bukan gambaran lengkap, beberapa perbedaan umum meliputi:

  • Definisi kehilangan tutupan hutan dan garis dasar pemantauan hutan: Meskipun data kehilangan tutupan pohon mencakup kehilangan semua jenis tutupan pohon akibat penyebab apa pun, sistem pemantauan nasional sering kali lebih ketat dalam menentukan jenis gangguan yang dimasukkan ke dalam statistik mereka dan dalam garis dasar yang digunakan untuk pemantauan hutan, karena mereka bertujuan mengukur deforestasi sesuai dengan definisi resmi. Misalnya, PRODES Brasil mengukur deforestasi hutan alam yang ditebang habis untuk pertanian, padang rumput, dan pertambangan, tetapi tidak memasukkan penebangan selektif atau kebakaran.
  • Luas area minimum yang diukur: Meskipun data kehilangan tutupan pohon menggunakan piksel berukuran 30 meter, sistem pemantauan nasional mungkin menggunakan unit pemetaan minimum yang lebih besar; misalnya, baik PRODES maupun SIMONTANA menggunakan unit pemetaan minimum sebesar 6,25 hektare.
  • Periode pelaporan: Meskipun periode pelaporan data kehilangan tutupan pohon mencakup tahun kalender, baik PRODES maupun SIMONTANA menggunakan periode pelaporan yang berbeda — PRODES mencakup Agustus hingga Juli, sedangkan SIMONTANA mencakup Juli hingga Juni.
  • Metode: Meskipun berbagai sistem pemantauan mungkin menggunakan citra satelit sebagai data masukan, metode yang digunakan untuk mendeteksi kehilangan dapat bervariasi. Data kehilangan tutupan pohon dihasilkan menggunakan algoritma otomatis untuk mendeteksi kehilangan berdasarkan citra satelit Landsat. Namun, baik PRODES maupun SIMONTANA menggunakan interpretasi visual manual terhadap citra satelit untuk menggambarkan kehilangan.

Perbedaan-perbedaan ini penting untuk dipertimbangkan saat menafsirkan statistik antar sistem pemantauan dan sering kali mengakibatkan perbedaan dalam luas area kehilangan yang dilaporkan setiap tahun oleh berbagai sistem.

Baca blog kami di Global Forest Watch untuk mengetahui lebih lanjut tentang detail dan perbedaan yang spesifik pada data terbaru.

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Dark surfaces absorb the rays from the sun (low albedo).\r\n"},"94":{"name":"biodiversity intactness","description":"The proportion and abundance of a location\u0027s original forest community (number of species and individuals) that remain.\u0026nbsp;\r\n"},"95":{"name":"biodiversity significance","description":"The importance of an area for the persistence of forest-dependent species based on range rarity.\r\n"},"142":{"name":"boundary plantings","description":"Trees planted along boundaries or property lines to mark them well.\r\n"},"98":{"name":"carbon dioxide equivalent (CO2e)","description":"Carbon dioxide equivalent (CO2e) is a measure used to aggregate emissions from various greenhouse gases (GHGs) on the basis of their 100-year global warming potentials by equating non-CO2 GHGs to the equivalent amount of CO2.\r\n"},"153":{"name":"climate domain","description":"Major ecosystem regions, summarized as boreal, temperate, tropical and subtropical.\u0026nbsp;"},"99":{"name":"CO2e","description":"Carbon dioxide equivalent (CO2e) is a measure used to aggregate emissions from various greenhouse gases (GHGs) on the basis of their 100-year global warming potentials by equating non-CO2 GHGs to the equivalent amount of CO2.\r\n"},"1":{"name":"deforestation","description":"The change from forest to another land cover or land use, such as forest to plantation or forest to urban area.\r\n"},"77":{"name":"deforested","description":"The change from forest to another land cover or land use, such as forest to plantation or forest to urban area.\r\n"},"76":{"name":"degradation","description":"The reduction in a forest\u2019s ability to perform ecosystem services, such as carbon storage and water regulation, due to natural and anthropogenic changes.\r\n"},"75":{"name":"degraded","description":"The reduction in a forest\u2019s ability to perform ecosystem services, such as carbon storage and water regulation, due to natural and anthropogenic changes.\r\n"},"79":{"name":"disturbances","description":"A discrete event that changes the structure of a forest ecosystem.\r\n"},"68":{"name":"disturbed","description":"A discrete event that changes the structure of a forest ecosystem.\r\n"},"65":{"name":"driver of tree cover loss","description":"The cause of tree cover loss, such as agriculture or urban development. 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Natural forests can be managed or unmanaged (see separate definitions).\u0026nbsp;"},"144":{"name":"open canopy systems","description":"Individual tree crowns that do not overlap to form a continuous canopy layer.\r\n"},"88":{"name":"planted","description":"Stands of trees established through planting, including both planted forest and tree crops."},"14":{"name":"planted forest","description":"Planted trees \u2014 other than tree crops \u2014 grown for wood and wood fiber production or for ecosystem protection against wind and\/or soil erosion.\r\n"},"73":{"name":"planted forests","description":"Planted trees \u2014 other than tree crops \u2014 grown for wood and wood fiber production or for ecosystem protection against wind and\/or soil erosion."},"148":{"name":"planted trees","description":"Stands of trees established through planting, including both planted forest and tree crops."},"149":{"name":"Planted trees","description":"Stands of trees established through planting, including both planted forest and tree crops."},"15":{"name":"primary forest","description":"Old-growth forests that are typically high in carbon stock and rich in biodiversity. 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Landscapes may be forested or non-forested."},"87":{"name":"seminatural","description":"Forest with predominantly native trees that have not been planted. Trees are established through silvicultural practices, including natural regeneration or selective thinning.FAO"},"59":{"name":"seminatural forests","description":"Forest with predominantly native trees that have not been planted. 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