Kentsel Yayılma Baskısı Altında Karbon Kaybı ve Karbon Tutulumunun Çevresel İzlenmesi: İstanbul, Türkiye Örneği

Öz

Hızla büyüyen megakentlerde kentsel yayılma, karasal karbon dinamiklerini önemli ölçüde değiştirmekte; çoğu zaman karbon tutma potansiyelini azaltırken sera gazı emisyonlarını artırmaktadır. Bu çalışma, 2017–2024 yılları arasında İstanbul, Türkiye’de arazi kullanım değişiminin karbon stokları üzerindeki etkilerini, Coğrafi Bilgi Sistemleri (CBS) çerçevesinde Entegre Ekosistem Hizmetleri ve Ödünleşimleri Değerleme Modeli (InVEST) kullanarak değerlendirmiştir. Sentinel-2 uydu görüntüleri ve denetimli sınıflandırma yöntemiyle altı ana arazi örtüsü sınıfı belirlenmiş ve mekânsal-zamansal geçişler nicel olarak ortaya konmuştur. Elde edilen bulgular, yapılı alanlarda %3,72’lik bir artış; tarım (–%2,03), orman (–%0,31) ve çayır-mera (–%0,19) alanlarında ise azalışlar olduğunu göstermiş ve bunun sonucunda –1.117.034,57 tC (yaklaşık –4,1 MtCO₂eşd.) düzeyinde net bir karbon kaybı meydana gelmiştir. Toplam kayıpların %75,7’sini oluşturan toprak organik karbonunun, özellikle tarım alanlarında en kırılgan karbon havuzu olduğu belirlenmiştir. Orman alanlarında gözlenen toprak ve yerüstü karbon kayıpları, ormansızlaşma ve geçirimsiz yüzey artışının olumsuz etkilerini daha da vurgulamaktadır. Bulgular, daha sıkı arazi kullanım düzenlemelerine, ekolojik tampon alanların korunmasına ve kentsel karbon yönetimini güçlendirmek amacıyla yeşil altyapının entegrasyonuna yönelik acil bir gereksinime işaret etmektedir. Bu çalışma, InVEST modelinin kentsel ölçekte karbon izleme ve karbon nötrlüğü hedeflerine ulaşmada karar destek aracı olarak uygulanabilirliğini ortaya koymaktadır.

Anahtar Kelimeler

• Karbon stoğu değişimi
• Yeşil altyapı
• InVest modeli
• Arazi kullanım değişimi
• Kentsel Yayılma

Environmental Monitoring of Carbon Loss and Sequestration under Urban Expansion Pressure: A Case Study from Istanbul, Türkiye

Öz

Urban expansion in rapidly growing megacities significantly alters terrestrial carbon dynamics, often reducing carbon sequestration potential and increasing greenhouse gas emissions. This study assessed the impacts of land-use change on carbon stocks in Istanbul, Türkiye, between 2017 and 2024, using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model within a Geographic Information Systems (GIS) framework. Sentinel-2 satellite imagery and supervised classification identified six major land cover classes and quantified spatial-temporal transitions. Results revealed a 3.72% increase in built-up areas and declines in agricultural (–2.03%), forested (–0.31%), and rangeland (–0.19%) areas, leading to a net carbon loss of –1,117,034.57 tC (approximately –4.1 MtCO₂eq). Soil organic carbon represented the most vulnerable pool, accounting for 75.7% of total losses, particularly in agricultural lands. Aboveground and soil carbon losses in forested areas further emphasized the adverse impacts of deforestation and impervious surface expansion. The findings highlight the urgent need for stricter land-use regulations, conservation of ecological buffer zones, and integration of green infrastructure to enhance urban carbon management. The study demonstrates the applicability of the InVEST model for urban-scale carbon monitoring and as a decision-support tool for achieving carbon neutrality targets.

Anahtar Kelimeler

• Carbon stock change
• Green infrastructure
• InVEST model
• Land-use change
• Urban expansion

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