RL-Driven Sustainable Land-Use Allocation for the Lake Malawi Basin
Organizations: Georgia Institute of Technology
Abstract
Unsustainable land-use practices in ecologically sensitive regions threaten biodiversity, water resources, and the livelihoods of millions. This paper presents a deep reinforcement learning (RL) framework for optimizing land-use allocation in the Lake Malawi Basin to maximize total ecosystem service value (ESV). Drawing on the benefit transfer methodology of Costanza et al., we assign biome-specific ESV coefficients -- locally anchored to a Malawi wetland valuation -- to nine land-cover classes derived from Sentinel-2 imagery. The RL environment models a 50x50 cell grid at 500m resolution, where a Proximal Policy Optimization (PPO) agent with action masking iteratively transfers land-use pixels between modifiable classes. The reward function combines per-cell ecological value with spatial coherence objectives: contiguity bonuses for ecologically connected land-use patches (forest, cropland, built area etc.) and buffer zone penalties for high-impact development adjacent to water bodies. We evaluate the framework across three scenarios: (i) pure ESV maximization, (ii) ESV with spatial reward shaping, and (iii) a regenerative agriculture policy scenario. Results demonstrate that the agent effectively learns to increase total ESV; that spatial reward shaping successfully steers allocations toward ecologically sound patterns, including homogeneous land-use clustering and slight forest consolidation near water bodies; and that the framework responds meaningfully to policy parameter changes, establishing its utility as a scenario-analysis tool for environmental planning.
Figures & tables
| Class | Type | ET (kg/m 2 /yr) |
|---|---|---|
| Water | Protected | 616.93 |
| Trees | Modifiable | 933.57 |
| Flooded | Protected | 767.62 |
| Crops | Modifiable | 675.66 |
| Built Area | Modifiable | 648.95 |
| Bare Ground | Modifiable | 591.53 |
| Class | Type | ESV | Ratio |
|---|---|---|---|
| (USD/ha/yr) | |||
| Water | Protected | 554 | 1.00 |
| Trees | Modifiable | 238 | 0.43 |
| Flooded | Protected | 1,136 | 2.05 |
| Crops | Modifiable | 246 * 1.35 = 332 | 0.60 |
| Built Area | Modifiable | 295 | 0.53 |
| Component | Symbol | Weight |
|---|---|---|
| Tree contiguity bonus | 1.0 | |
| Crop contiguity bonus | 4.0 | |
| Built-area contiguity bonus | 2.0 | |
| Water buffer penalty | 6.0 (anneal ) | |
| Riparian-tree bonus | 5.0 |
Appendix figures & tables2 assets
Supplementary material from the paper’s appendix.
Appendix
| ExpI | ExpII | ExpIII | |
|---|---|---|---|
| Eco-only | Spatial-without-regen | Headline (Spatial+Regen) | |
| Dominant conversion | Built | Mixed | Crops |
| Forest near water | Not obvious | Increased | Increased |
| Built expansion | Aggressive | Clustered | Clustered, restrained |
| Crop allocation | Moderate | Moderate | High |
| Ecological realism | Low | High | High |
| Parameter | Value |
|---|---|
| Learning rate | (last 33%) |
| Rollout length ( ) | 2,048 |
| Mini-batch size | 128 |
| PPO epochs | 10 |
| Discount ( ) | 0.99 |
| GAE | 0.95 |