Urbanization and Decline of Old Growth Windbreak Trees on Private Homesteads: A Case Study in Ryukyu Island Villages, Japan

Bixia Chen

doi:10.3390/f11090990

Abstract

Urban trees are under unprecedented pressure and competition worldwide with other land uses. Homestead windbreaks in urban areas are an important part of urban forests because of their proximity to settlements. To aid in the conservation of old-growth homestead trees in the urban setting on Ryukyu Archipelago, Japan, this article surveys the dimensions and spatial distribution of century-old trees planted as windbreaks along homestead borderlines on Ishigaki Island in the Ryukyu Archipelago and the historical change caused by urban sprawl. The homesteads studied in this article do not match the scale of a traditional Western context and usually consist of an area of less than 200 square meters on Okinawa. A combined approach consisting of field surveys and the study of aerial photos was applied to identify changes in spatial distribution of tree lines surrounding the houses in 1945, 1972 and the present. We measured the dimensions of 1659 Fukugi trees with a minimum diameter at breast height (DBH) of 5 cm. The mean tree height, mean DBH and mean estimated tree age were 7.3 m, 26.9 cm and 107.5 years, respectively. Homestead trees are not only useful as windbreaks, timber sources and musical instruments, but have also been historically resilient in the face of strong typhoons and catastrophic tsunamis in the region. Over 60% of the surveyed trees were planted on the east and north sides of homesteads as protection from typhoons and monsoonal winds in the winter. In addition to G. subelliptica, other tree species, namely Podocarpus macrophyllus and Diospyros egbert-walkeri, have been commonly used as homestead windbreaks. However, homestead windbreaks in highly urbanized regions are generally declining and have experienced fragmentation, lower tree density and shorter tree height than those in rural areas. Because of the small number of trees older than 200 years, we assume that high urbanization has jeopardized old-growth trees. The demand for settlement land dramatically increases as the population increases and household-size decreases, creating more households. Therefore, a conservation project involving multiple stakeholders must be developed to conserve old-growth trees in urban settings.

Highlights

The homestead windbreak landscape on the Ryukyu Islands, established approximately 300 years ago, is an important part of urban forests and residential landscapes, as its proximity to human settlements, and which provides psychological, sociological, and esthetic benefits
We recently extended our survey of the remaining Fukugi trees to the Yaeyama Island group—the southernmost islands in the Okinawa Prefecture—to clarify the dimensions and spatial distribution of the remaining homestead trees on isolated land and coastal villages
Homestead in highly urbanized regions are in decline fragmentation, Homesteadwindbreaks windbreaks in highly urbanized regions are and in experience decline and experience lower tree density and tree shorter tree height compared previous surveytosites on Okinawa fragmentation, lower density and shorter tree to height compared previous surveyand sitesthe on Okinawa and the Ishigaki Islands [32,33,34,43]

Summary

Introduction

The homestead windbreak landscape on the Ryukyu Islands, established approximately 300 years ago, is an important part of urban forests and residential landscapes, as its proximity to human settlements, and which provides psychological, sociological, and esthetic benefits. The remaining old-growth homestead trees on private residential parcels have been largely neglected by the administration in Japan [1]. Natural hazards and fast urbanization affect the removal of planted trees in the central cities of the Okinawa Prefecture. Forests 2020, 11, 990 conservation program exists in the Okinawa Prefecture because of private land ownership [2], which allows homeowners to dispose of trees freely without legal regulations or the responsibility to secure good care and management for the trees. An appropriate conservation scheme must be established to conserve traditional residential landscapes and old-growth windbreaks

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Discussion

Conclusion