After the double whammy of Hurricane Ike in 2008 and the great Texas drought of 2011, the unthinkable happened in Houston’s Memorial Park: Half of the trees died. An urban woodland covering 1,503 acres in the heart of the city was suddenly a wasteland.
This catastrophe prompted the Houston Arboretum and Nature Center, established in 1951 on 155 acres in the southwest quadrant of Memorial Park, to commission a new master plan in 2012. Its intent was to understand how such a disaster could have occurred and how to prevent another one in the future. A large multidisciplinary team led by Steven Spears and and Rebecca Leonard of Design Workshop, an Austin-based landscape architecture, planning, and urban design firm, in collaboration with Reed Hilderbrand Landscape Architecture, conducted extensive forensic research to determine the cause of mortality. What they found was intriguing.
According to their reports, the natural state of Memorial Park (and, by extension, much of Houston) was mostly prairie and savannah, with riparian and woodland ecosystems restricted to the bayou banks. Before Anglo-American settlement, a combination of droughts, grazing, and fires maintained equilibrium between these biomes. By the beginning of the 20th century this system was disrupted when wild, grazing herds were killed off, natural fires were quickly extinguished, and even drought was mitigated by artificial irrigation. Trees and fast-growing underbrush, many species of which included such non-native and invasive species as yaupon, cherry laurel, Chinese tallow, poison ivy, and grapevines, proliferated beyond their former boundaries. Prairie grasses, now in shade, retreated. The change was rapid and profound. When Memorial Park was established in 1925, contemporary newspaper accounts reported breathlessly on Houston’s “forest playground,” not its “prairie playground.”
The study leading up to the master plan’s proposals analyzed historical accounts, soil conditions, drainage patterns, and the subtle micro-topography that modulated even the flattest areas of the site. It concluded that the areas of highest canopy mortality were in zones where former prairie land had been colonized by forest. These areas began at the edge of the riparian zone, along Buffalo Bayou, which forms the arboretum’s southern edge, and extended to the north and easternmost boundaries of the site. The shock of hurricane and extreme drought in close succession was in reality a long-overdue, natural resetting of the local ecology: What modern Houstonians had postponed for over a century was undone in this 36-month period.
The new master plan seeks to educate Houstonians about the region’s historical natural environment by recreating the delicate interplay of ecosystems formerly occurring across the arboretum’s site. To achieve this, its main effort is to reestablish a significant prairie and savannah component. Prior to the drought, 30 percent of the site was riparian, 65 percent was woodland, and a mere 3.5 percent was prairie. The new landscape design proposes a more evenly balanced mixture of 31 percent riparian, 26 percent woodland, and 40 percent prairie and savannah. The riparian areas along Buffalo Bayou and a ravine at the northwest corner of the site will remain mostly within their current boundaries. The biggest change will be on the remaining two thirds of the site, where a series of long, narrow “fingers” of woodland will intersect the new prairie and savannah.
This woodland corridor scheme was selected over two other options — prairie clearings in a continuous woodland and groves of woodland in a continuous prairie — for practical and aesthetic reasons. The corridors provide the longest boundaries between ecosystems. These transitional areas, which blend characteristics of their adjacent biomes, are called ecotones and provide vital animal habitats and foraging areas. The fluid arrangement of the woodland corridors also corresponds to the areas where mature forest trees survived beyond the historic woodland zone. Visually, according to Spears, these corridors will create long and controlled views of prairie and forest, which will allow for greater spatial richness across the site.
Complementing the new landscape will be new buildings and a reconfigured trail system through the arboretum. Lake|Flato Architects of San Antonio designed a new visitor center and a separate education center, incorporating the existing visitor’s building designed by Houston architect Hugo V. Neuhaus, Jr. in 1968 near Woodway Drive. These new buildings, long and thin, are equipped with luxuriously large covered porches and overhanging roofs. A more discreet maintenance and bus parking facility will be located to the south of the public buildings off the 610 Loop side of the site. The trails will highlight the different ecosystems as they thread through the site with a mixture of grade-level paths and raised boardwalks.
The multiphase reconfiguration of the arboretum will require decades to complete, with a maturation period of some 30 years. In the meantime, especially during the first phases, the arboretum will look like a battlefield as dead trees are pulled down, undesirable species are culled, and the land is prepared for new plants.
While it is clear that something has to be done to address the crisis situation in the arboretum, the creative destruction necessary to implement the master plan gives rise to some questions. With both grazing herds and natural fires permanently removed as ecological balancing factors, what kind of historical authenticity can the site truly maintain? What lessons will visitors ultimately come away with by viewing a site whose newly “natural” appearance must first be created, then maintained, by significant human intervention? Considering that the site has not existed in its pre-human state for many generations, might it be of value to address this new and changed condition, rather than to reintroduce ecosystems, however historically significant, that cannot exist independently under today’s environmental conditions? Finally, how does going back to a pre-urban state address the future of the environment in a modern city like Houston during a period of what will likely be rapidly-changing climatic conditions? The key to the success of the master plan, it seems, will be how it navigates away from the pull of an easy nostalgia to avoid becoming a fictionalized, landscape version of a Colonial Williamsburg. The educational program of the arboretum should clearly acknowledge that, while the newly reinstalled ecosystems are an artifice, their lessons of sustainability, resource management, and conservation remain ever compelling.
Ben Koush is an architect in Houston.
Originally published in the March/April 2015 issue of Texas Architect.