Background
Colombo wetlands (CW) are the last ecological frontier of the Sri Lankan National capital. CW network has Classified as the most vulnerable ecosystem under the Ramsar convention which suffered from severe fragmentation due to human encroachments and urban densifications. Over the past few decades, 31% of habitat loss resulted in the dislocation and extinction of many species in the wetland forest. Currently, restoration efforts are taking place to rehabilitate the ecology through wetland parks and ecological patches. However, promotion of the species movement is not evident through the development of isolated patches due to fewer considerations of the connectivity in the Urban matrix. Therefore, management of ecological network connectivity is a predominant measure to rehabilitate the CW habitats. Even though the literature suggests that patch metrics are a vital threshold to predict the species flow rates, lack of scientific research involved in such phenomenon in Sri Lanka. Thus, this study experimentally investigates the role of ecological patch metrics towards connectivity index in Colombo urban wetlands. The study equips remote sensing data 2018 to calculate the wetland patch metrics (Configuration) of Total area (TA), Total edge (TE), Shape Index (SI), Core area index (CAI), and Inter-patch distances (IPD) for 3 sample locations. GIS modeled Least cost paths within CW boundaries are acquired to calculate the Species flow Index (SFI) per patch for common species.
Results
The Pearson correlation test explicitly proves that (P< 0.05) the SFI co-related with TA, TE, CAI, and IPD. A strong positive correlation was observed in patch metrics of TA, TE, and CAI and a strong negative in IPD against SFI. Furthermore, based on connectivity contributions, the study proposed three wetland patch classifications as open patches, closed patches, and active patches the which are rated upon the species flow.
Conclusion
In city-level implications, improvement of total area, perimeter, and reduction of interpatch distance for “active wetland patch” will result in re-gaining the species flow for Colombo wetlands. The overall study is an applied model for restoring urban ecological networks to gain maximize connectivity index to preserve species richness in urban ecological networks.