Changes in land cover and grassland area over the past 120 years in a rapidly urbanised area in Japan

Abstract

In wet temperate regions, human activity has played an important role in shaping the size and distribution of grasslands. We examined change in land cover type and grassland area in a 9.2 × 22.3 km area of northern Chiba Prefecture, based on historical maps and documents for four time periods (1880s, 1950s, 1980s and 2000s). In the 1880s, conifer forests occupied the largest area (43.1%) amongst land cover types and grasslands accounted for 4.2% of the total area. However, literature available from the 1880s suggests that the understorey of conifer forests may have served as additional habitat for grasses. Thus, the habitat of grassland species is suggested to have covered up to 54% of the study area during this time period. By the 1950s, much of the grassland present in the 1880s had been changed to agricultural fields and paddies and grassland area had reduced to 2.9%. Residential development prior to and during the 1980s led to the conversion of forests and agricultural fields to grassland, increasing the grassland area to 11.6% of the study area. Finally, in the 2000s, grasslands had declined to 6.0% of the study area, likely due to conversion to residential areas. Despite these changes over time, 1.5% of the study area has remained as native forest or grassland for over 120 years. The spatial data presented herein are useful for conservation planning and studying the effect of historical land use change on biodiversity.

Plant community assembly in suburban vacant lots depends on earthmoving legacy, habitat connectivity, and current mowing frequency

“…Cousins (2009) found that time-delayed response is detected in regions where contemporary landscapes retain >10% of traditional habitats. As our study region maintains only 2.8% of remnant grasslands of those in 1880s (Noda et al, 2019), delayed responses may not have been observed.…”

“…Grasslands in this region had historically been maintained as a pasture for warhorses, but since the middle of 19th century began to be changed to coppice woodlands dominated mainly by pine trees (Miyamoto & Yokohari, 2010). Due to frequent tree cutting, the coppice in these landscapes was generally sparse with short trees, allowing grassland-like vegetation to persist until the 1960s (Koyanagi, Kusumoto, Yamamoto, & Takeuchi, 2012b;Noda, Kondoh, & Nishihiro, 2019). After this, suburban development took place and earthmoving accompanied by topsoil removal and ground leveling was carried out in this region.…”

Temporal Continuities of Grasslands and Forests as Patches of Natural Land in Urban Landscapes: A Case Study of the Tsukuba Science City

“…The pattern of replacement of forests and grasslands to residential areas is typical at the scale of the prefectures surrounding the study site [27,31,61]. Generally, in Japan's metropolitan areas, urban sprawl aggravated the farming environment.…”

“…A number of studies point out that biodiversity richness was affected by decades of habitat connectivity, particularly in human-maintained grasslands, which are symbolic human-modified landscapes [15,[56][57][58][59][60]. It is necessary to prioritize certain conservation goals by investigating historical land cover transitions and maintaining continuity, including in the context of urban nature [6,61]. Therefore, the urban green space patches that replaced grassland-like environments that were under the control of rural communities are important as a remnant for human-modified landscapes.…”

“…The results of the interviews also suggest that the forests as an agricultural landscape before the 1960s had the characteristics of a grassland environment. Therefore, even if the clustered areas were classified as "Forest" in the 1880s, there can be essential cases of grassland biodiversity [61]. Because grasslands in Japan cannot be maintained without continued management, the conservation of these grasslands, such as the grasslands in the HEARO, may be highly valuable even though their top soils were modified decades ago.…”