← Back to Calculator

📚 Methodology & Theory

Understanding the science behind carbon sequestration calculations

🎯 Overview

This calculator estimates the new forest and coastal area required through reforestation and restoration to achieve Indonesia's 2050 carbon reduction targets. The methodology is based on the IPCC 2006 Guidelines for National Greenhouse Gas Inventories, specifically Volume 4 (Agriculture, Forestry and Other Land Use - AFOLU), using Tier 1 methodology.

Key Assumption: Existing mature forests are at carbon equilibrium (they absorb roughly as much CO₂ as they release). To achieve net additional sequestration, we must plant new forests that are actively growing.

🔢 Core Calculation Formula

The calculator follows this step-by-step process:

Step 1: Calculate Total Reduction Needed

Total_Reduction = Emissions_2030 - Target_2050

Example: 1,200 MtCO₂e - 540 MtCO₂e = 660 MtCO₂e reduction needed

Step 2: Calculate Sequestration Target

Sequestration_Target = Total_Reduction × Sequestration_Percent

Example: 660 MtCO₂e × 25% = 165 MtCO₂e from sequestration

Step 3: Calculate Effective Sequestration Rate

Effective_Rate = Base_Rate × (1 + Root_Ratio) × (1 - Risk_Factor)

Example: 7.0 tCO₂/ha/yr × 1.26 × 0.80 = 7.06 tCO₂/ha/yr

Step 4: Calculate Weighted Average Rate

Weighted_Rate = (Forest% × Forest_Rate) + (Coastal% × Coastal_Rate)

Example: (80% × 7.06) + (20% × 9.45) = 7.54 tCO₂/ha/yr

Step 5: Account for Forest Degradation Loss

Degradation_Loss = Existing_Area × Cumulative_Loss_Factor × Rate

With 2% annual degradation over 20 years, ~33% of existing forest capacity is lost. New forests must compensate for this loss.

Step 6: Calculate Total Area Needed

Total_Area = (Sequestration_Target + Degradation_Loss) / (Weighted_Rate × Years)

Final calculation of hectares needed for new reforestation/restoration.

📊 IPCC Default Parameters

Sequestration Rates (Tier 1)

Ecosystem Type Rate (tCO₂/ha/yr) Source
🌲 Tropical Rainforest (Land) 7.0 IPCC 2006, Table 4.9
🌊 Coastal/Mangrove 7.5 IPCC Wetlands Supplement

Below-Ground Biomass

Parameter Value Meaning
Root-to-Shoot Ratio 0.26 Roots add 26% more carbon storage to above-ground estimate

Indonesia-Specific Data

Parameter Value Source
Current Forest Area 120,343,230 ha Indonesia 2022 Forest Statistics
Coastal/Mangrove Area 3,364,080 ha Indonesia Mangrove Alliance
2030 Emissions Baseline 1,200 MtCO₂e Indonesia NDC 2022
2050 Target 540 MtCO₂e Indonesia Net-Zero Roadmap

⚠️ Risk Scenarios

Not all planted forests will survive until maturity. The risk factor accounts for potential losses from:

Scenario Risk Factor Interpretation
🟢 Optimistic 0% Best case: all planted forests survive and sequester at full capacity
🟡 Moderate 20% Realistic: standard losses from natural disturbances
🔴 Pessimistic 40% Worst case: high losses from combined stressors

📉 Forest Degradation Model

The degradation rate parameter models the annual decline in existing forest carbon sink capacity due to:

Compound Degradation Formula

For each year i = 1 to N: Annual_Loss[i] = Remaining_Capacity × Degradation_Rate Remaining_Capacity -= Annual_Loss[i] Cumulative_Loss += Annual_Loss[i]

With 2% annual degradation over 20 years:
Cumulative loss ≈ 1 - (1 - 0.02)²⁰ ≈ 33% of original capacity

Important: This carbon loss from degrading existing forests must be replaced by new forests, in addition to achieving the original sequestration target.

🔬 Limitations & Assumptions

Recommendation: Use this calculator for scenario exploration and policy discussion, not for precise national inventory accounting. For official purposes, consult Indonesia's National Forest Monitoring System (NFMS).

📚 References