Development of spontaneous vegetation on reclaimed land in Singapore measured by NDVI

Abstract

Population and economic growth in Asia has led to increased urbanisation. Urbanisation has many detrimental impacts on ecosystems, especially when expansion is unplanned. Singapore is a city-state that has grown rapidly since independence, both in population and land area. However, Singapore aims to develop as a ‘City in Nature’, and urban greenery is integral to the landscape. While clearing some areas of forest for urban sprawl, Singapore has also reclaimed land from the sea to expand its coastline. Reclaimed land is usually designated for future urban development, but must first be left for many years to stabilise. During the period of stabilisation, pioneer plant species establish, growing into novel forest communities. The rate of this spontaneous vegetation development has not been quantified. This study tracks the temporal trends of normalized difference vegetation index (NDVI), as a proxy of vegetation maturity, on reclaimed land sensed using LANDSAT images. Google Earth Engine was used to mosaic cloud-free annual LANDSAT images of Singapore from 1988 to 2015. Singapore’s median NDVI increased by 0.15 from 0.47 to 0.62 over the study period, while its land area grew by 71 km2. Five reclaimed sites with spontaneous vegetation development showed variable vegetation covers, ranging from 6% to 43% vegetated cover in 2015. On average, spontaneous vegetation takes 16.9 years to develop to a maturity of 0.7 NDVI, but this development is not linear and follows a quadratic trajectory. Patches of spontaneous vegetation on isolated reclaimed lands are unlikely to remain forever since they are in areas slated for future development. In the years that these patches exist, they have potential to increase urban greenery, support biodiversity, and provide a host of ecosystem services. With this knowledge on spontaneous vegetation development trajectories, urban planners can harness the resource when planning future developments.

Beyond Park Boundaries: Exploring The Effect of Surrounding Land Use on Sound Levels of ParksBeyond Park Boundaries: Exploring The Effect of Surrounding Land Use on Sound Levels of Parks

“…This suggests that the park environment of KLCC Park offers great contrast from its dense urban surroundings. Likewise, in Singapore, the NDVI of urban areas ranges from 0.4 -0.6, indicating a high vegetation coverage across the city (Gaw et al, 2021). Therefore, in comparison, the role of parks in Malaysia are more evident as a space for getaway of the urban environment and demonstrates a higher significance on the reductions of urban sound levels in the parks.…”

Denser and greener cities: Green interventions to achieve both urban density and nature

“…This kind of vacant land is not common in a densely settled city like Singapore, although the restoration of streams that were previously lined with concrete like in Bishan‐Ang Mo Kio Park is one example. Another example in Singapore is reclaimed land, which may be allowed to naturally reforest for several decades even if it is ultimately slated for development for housing (Gaw & Richards, 2021). In many shrinking or deindustrialized cities like Detroit, there is more vacant land that can be reused.…”

Which index is better for assessing the success of reclamation: Naturalness or hemeroby?

“…Plant communities can be created especially on reclamation sites (Bauman et al, 2015) or be the result of spontaneous self-growth, as is the case on abandoned lands (Gaw & Richards, 2021). Spontaneous vegetation succession can be useful for restoring sites after mining (Prach et al, 2001), but it is very rarely used due to its low predictability (Mudrák et al, 2016).…”