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GLAM Vegetation Mapping: Gowanus Low Altitude Mappers focus on biodiversity

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Published in 2013 Grassroots Mapping Forum#4. Order a copy or subscribe online.

written by Gena Wirth and Hans Hesselein

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The watery corridor of the Gowanus Canal hosts plants and animals adapted to survive, maybe even flourish, in an other-worldly environment. In the Gowanus, elements of a healthy ecosystem are transformed by human occupation. Life-giving water is reduced to a thick sludge, dotted with floating sewage and petroleum slicks. Soil is replaced by industrial development, layers of asphalt, concrete and landfill dumped along the canal edge. The conditions for growth don’t appear to exist, yet the Gowanus Canal continues to host life.

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2012 December 25 - Native night heron (Nycticorax nycticorax ) in a synanthropic (human adapted) Gowanus Canal Chinese Empress Tree (Paulownia tomentosa). (photo by Shan Jayakumar)

The Gowanus Canal Conservancy (GCC) Vegetation Mapping Project examines this urban ecology of the canal edges and identifies just what succeeds here and why. While the contributions of adjacent urban ecosystems--Prospect Park, Greenwood Cemetery, even street trees--are increasingly well documented, the Gowanus Canal remains off the map and its ecological presence undocumented. We aim to identify the species that thrive along the canal and locate them in time and space, relative to the microclimates of the canal edges’ proximity to salty water, sun and shade tolerance, soil conditions, flood resilience, ability to thrive in varied soil conditions.

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2012 June 24 – Gowanus crack ecology: Grass growing through paving stones at the Gowanus Canal Bayside Fuel Depot. Mapping vegetation patterns such as these uncover ecological clues for landscape opportunities and more water sensitive urban design. (photos by Eymund Diegel)

This is a huge undertaking, so we have started small. In Fall of 2012, a team of balloon mappers led the first grassroots mapping vegetation assessment of the Salt Lot Berm Garden, a four hundred foot stretch of the Gowanus partially maintained by the GCC. Capturing images from a low altitude of 30’ to 100’ in height, we created a high resolution collage of the Berm Garden vegetation with enough detail to identify plant material. Tree, shrub, perennial, and select groundcover vegetation visible in the imagery were identified through comparison with ground photos. Late fall made particular species quite distinct, notably the urban species such as Tree of Heaven /Ailanthus altissima, whose orange and red seedheads were visible during the flight and rendered this tree distinct from Rhus typhina, another urban colonizer with compound leaf structure that appears similar from above. Certain volunteer groundcovers, such as Queen Anne’s Lace / Daucos carota, were in bloom, with its umbrella-like flower structure creating recognizable patterns on the ground. The Berm Garden is a mix of volunteer and intentionally planted species--the aerial maps give a glimpse into the impact of the GCC plantings, the success rate and health of the introduced species, and reveals potential sites for further intervention.

Guided by canoe in the canal waters, the balloon crosses physical and perceptual barriers at the ground level and digitally fills in the gap between the on-the ground experience and the readily available Google Earth view. Balloon mapping, combined with (not yet) publically available LIDAR data, has the potential to not only document species type and location, but plant size and height. Aided by our work, questions that until now could only be answered through a laborious survey or expensive aerial imagery are now within reach. How diverse and how large is the canal’s urban forest? What is the composition of native and non-native species? What plant communities are underrepresented and which are thriving? How can we quantify the current ecological benefits of this unknown urban ecosystem?

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2011 September – Goldenrod (Solidago sempervirens) and bees at the Gowanus Canal Salt Lot garden, with oil slicks from historical Manufactured Gas Plants. (photo by Sean Hanley)

It is clear that the Gowanus will change dramatically in the future. Superfund cleanup aims to remove and contain the contaminants in the canal sediment. Development pressures are visible along the canal edges and will likely skyrocket in the coming years as Superfund progresses. Adaptive, smart technologies are being prototyped to reduce combined sewer overflow events into the canal, further enhancing ecological conditions. In short, the future of the Gowanus is bright.

We aim to watch and document this transition, to understand this ecosystem over the coming years. Environmental clean-up and restoration are not always delicate procedures-- much of the successful vegetation we see today has the potential to be replaced with a more managed and manicured ecology. The abandoned “Brownfields” are often the greenest spots visible on the Balloon Aerials. The Low Altitude Vegetation Mapping Program is capturing historical ecological data benchmarks – helping gain new insights into what is truly “green” planning as landscapes change.

The wilds of the Gowanus are a place like no other- through the intentional documentation of what exists today we aim to influence the transformation of this urban landscape in an intelligent and ecologically relevant direction.

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2012 July – Gowanus Canal Conservancy Balloon Photograph of the abandoned Bayside Fuel Depot, currently the greenest and most planted spot on the Gowanus Canal. This “brownfield” may become less “green” after it is cleaned and redeveloped into condos.

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March 2013 – Honey Bee workshop on the banks of the Gowanus Canal Superfund site. Volunteers make reed hives and install them in self-seeded Tree of Heaven (Ailanthus altissima) groves to attract insects back to the Canal.

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2013 October 29 - Oil Ponding at the next of Sackett St after flood next to Bayside fuel depot. Naturally occuring oil filter: Certain plants that have adapted to the high pollution and stress levels of industrial street ecologies should be integrated into the landscape planning process.