Sentinel Trees Research Articles

Advocating for Ecoartivism: Sculpting sustainable choice with nature-based solutions

This paper presents the term Ecoartivism, for a novel nature-based strategy to address ecocide. Ecoartivism evolved from my ecoart practice, which sought pragmatic answers to chaotic environmental conditions. I advocate for how Ecoartivism draws from many influences to embrace a more intuitive but sustainable relationship between art, science, and law based on our values. I will track how my practice began layering basic aesthetic skills with science to restore degraded ecosystems, (Ghost Nets and Blue Rocks 1990–2005); inspired an original premise, trigger point theory, that small points of deliberate intervention can effect systemic change; and led to an Ecoartivist symphony and then an opera, (Blued Trees (2015 - present). My thinking has felt informed by Traditional Environmental Knowledge (TEK) and what some Indigenous communities term reciprocity, the idea that humans must live with mutual respect and as part of an inclusive vision of nature. Blued Trees developed a novel legal theory about ownership and what we choose to value. That redefinition led to Ecoartivism as a nature-based solution to sustainability. GPS located sentinel trees were identified as tree-notes in an aerial "score" composed of 1/3-mile increments across North America in forested corridors where natural gas pipeline installations were proposed. In a 2018 mock trial an injunction was handed down in favor of protecting the Blued Trees project on the basis of standing (a legal term establishing formal rights for due consideration in a court trial). I will explain how trigger point theory could support legal standing for Earth rights and ecosystem resilience. Blued Trees continues as an opera-in-progress to expand and deepen arguments for making ecocide accountable with serious penalties at the International Court of Justice at the Hague. This discussion will illustrate how ecoartivist strategies may support habitat contiguity, inspire and drive novel nature-based solutions to ecocide, deepening partnerships with scientists who can test and build on provocative insight.

Airborne multispectral imagery and deep learning for biosecurity surveillance of invasive forest pests in urban landscapes

Urban and peri-urban trees in major cities provide a gateway for exotic pests and diseases (hereafter “pests”) to establish and spread into new countries. Consequently, they can be used as sentinels for early detection of exotic pests that could threaten commercial, environmental and amenity forests. Biosecurity surveillance for exotic forest pests relies on monitoring of host trees — or sentinel trees — around high-risk sites, such as airports and seaports. There are few publicly available spatial databases of urban street and park trees, so locating and mapping host trees is conducted via ground surveys. This is time-consuming and resource-intensive, and generally does not provide complete coverage. Advances in remote sensing technologies and machine learning provide an opportunity for semi-automation of tree species mapping to assist in biosecurity surveillance. In this study, we obtained high resolution (≥12 cm), 10-band, multispectral imagery using the ArborCam™ system mounted to a fixed-wing aircraft over Sydney, Australia. We mapped 630 Pinus trees and 439 Platanus trees on-foot, validating their exact location on the airborne imagery using an in-field mapping app. Using a machine learning, convolutional neural network workflow, we were able to classify the two target genera with a high level of accuracy in a complex urban landscape. Overall accuracy was 92.1% for Pinus and 95.2% for Platanus, precision (user’s accuracy) ranged from 61.3% to 77.6%, sensitivity (producer’s accuracy) ranged from 92.7% to 95.2%, and F1-score ranged from 74.6% to 84.4%. Our study validates the potential for using multispectral imagery and machine learning to increase efficiencies in tree biosecurity surveillance. We encourage biosecurity agencies to consider greater use of this technology.

Interception Strategies for Managing Exotic Ambrosia Beetles (Coleoptera: Curculionidae) in Nurseries

Interception Strategies for Managing Exotic Ambrosia Beetles (Coleoptera: Curculionidae) in Nurseries

Southern Range Expansion of the Emerald Ash Borer, Agrilus planipennis, in Russia Threatens Ash and Olive Trees in the Middle East and Southern Europe

Agrilus planipennis (Coleoptera: Buprestidae) is the most serious invasive pest of ash trees (Fraxinus spp., Oleaceae) in the world. It has not yet reached the range of olive tree plantations, however it has been shown to complete its life cycle in this host tree. This pest native to East Asia was first found in Europe in Moscow in 2003 and has been spreading ever since. The aims of this study were to determine if the southern border of the range has already reached the Caucasus and to assess the potential range in this region based on host availability and heat availability. In 2021, we surveyed ash trees south to the known range in Russia. We did not find the pest in six cities in the North Caucasus region but found it in the city of Azov close to the Caucasus. Analysis of information about 550 localities of ash trees in the Caucasus showed that Fraxinus spp. is common throughout the region. The calculation of annual growing degree days base 10 °C indicated that the places where Fraxinus spp. grow above 1500 m are too cold for A. planipennis and therefore could potentially become a refuge for ash trees. The spread of A. planipennis to the Caucasus is of concern. First, the forest ecosystems of this region are endangered, since European ash Fraxinus excelsior is much more common there than in the currently infested regions in Russia. Second, the Russian Caucasus can become the gateway to Georgia, Armenia, Azerbaijan, Turkey and other countries of the Middle East and Southern Europe. We propose using Fraxinus angustifolia, F. ornus and Olea europaea growing in the Caucasus and adjacent regions as sentinel trees for the monitoring and pest risk assessment of these tree species.

Scientists plant ‘sentinel trees’ to warn of devastating pests

Scientists plant ‘sentinel trees’ to warn of devastating pests

Trap Tree and Interception Trap Techniques for Management of Ambrosia Beetles (Coleoptera: Curculionidae: Scolytinae) in Nursery Production.

The majority of wood-boring ambrosia beetles are strongly attracted to ethanol, a behavior which could be exploited for management within ornamental nurseries. A series of experiments was conducted to determine if ethanol-based interception techniques could reduce ambrosia beetle pest pressure. In two experiments, trap trees injected with a high dose of ethanol were positioned either adjacent or 10-15 m from trees injected with a low dose of ethanol (simulating a mildly stressed tree) to determine if the high-dose trap trees could draw beetle attacks away from immediately adjacent stressed nursery trees. The high-ethanol-dose trees sustained considerably higher attacks than the low-dose trees; however, distance between the low- and high-dose trees did not significantly alter attack rates on the low-dose trees. In a third experiment, 60-m length trap lines with varying densities of ethanol-baited traps were deployed along a forest edge to determine if immigrating beetles could be intercepted before reaching sentinel traps or artificially stressed sentinel trees located 10 m further in-field. Intercept trap densities of 2 or 4 traps per trap line were associated with fewer attacks on sentinel trees compared to no traps, but 7 or 13 traps had no impact. None of the tested intercept trap densities resulted in significantly fewer beetles reaching the sentinel traps. The evaluated ethanol-based interception techniques showed limited promise for reducing ambrosia beetle pressure on nursery trees. An interception effect might be enhanced by applying a repellent compound to nursery trees in a push-pull strategy.

Improved biosecurity surveillance of non-native forest insects: a review of current methods

Biosecurity surveillance has been highlighted as a key activity to discover non-native species at the initial stage of invasion. It provides an opportunity for rapidly initiating eradication measures and implementing responses to prevent spread and permanent establishment, reducing costs and damage. In importing countries, three types of biosecurity activities can be carried out: border surveillance targets the arrival stage of a non-native species at points-of-entry for commodities; post-border surveillance and containment target the establishment stage, but post-border surveillance is carried out on a large spatial scale, whereas containment is carried out around infested areas. In recent years, several surveillance approaches, such as baited traps, sentinel trees, biosurveillance with sniffer dogs or predatory wasps, electronic noses, acoustic detection, laser vibrometry, citizen science, genetic identification tools, and remote sensing, have been developed to complement routine visual inspections and aid in biosecurity capacity. Here, we review the existing literature on these tools, highlight their strengths and weaknesses, and identify the biosecurity surveillance categories and sites where each tool can be used more efficiently. Finally, we show how these tools can be integrated in a comprehensive biosecurity program and discuss steps to improve biosecurity.

Modern approaches for early detection of forest pathogens are sorely needed in the United States

AbstractCurrent plant regulatory protocols rely on lists of known pathogens, but many forest pathogens are unknown. Live plants are inspected at port of entry for disease symptoms, but many plant pathogens can persist asymptomatically. Current efforts should be expanded by including random sampling of both symptomatic and asymptomatic plant tissues. Molecular probes and standardized protocols could be developed for invasive forest pathogens of most concern to the United States. High‐throughput sequencing (also known as next‐generation sequencing, or NGS) and bioinformatics could be used to identify potential pathogens in plant and soil samples collected at ports of entry from sentinel trees planted abroad, or in biosurveillance efforts. If potentially invasive forest pathogens were to be identified at ports of entry, sentinel trees, or with biosurveillance, this information must be shared with agencies that conduct forest health monitoring surveys beyond ports of entry.

The unique role of sentinel trees, botanic gardens and arboreta in safeguarding global plant health

The ever increasing threat from new and emerging plant pests and pathogens poses a significant threat to plant health on a global scale. Once an organism is introduced and establishes itself in a new region, it is incredibly costly, both in terms of environmental impact and economic loss, to manage it. In most cases, eradication and containment programmes are most effective when the organism is identified early on. Further to this, the most cost effective management of all is preventing introduction in the first place. Therefore, the role for early warning systems in plant health is becoming more evident. Botanic gardens and arboreta are unique resources that can help provide such early warning and are, currently, often overlooked within plant health. The staff and volunteers that work within these botanical institutes are knowledgeable and passionate people, who if made aware of current threats, can become additional ‘eyes and ears’ for first detection of new introductions. Gardens can also help to increase available information on organisms and, potentially, identify the ‘unknown’ organisms through sentinel research. Plant collections provide a large range of exotic hosts (so-called ‘sentinels’) growing in diverse regions around the world which can be studied to determine susceptibility to potential pests that have not been introduced to their native ranges. The International Plant Sentinel Network (IPSN) has been developed in order to support such work and bring together botanical institutes with organisations working within plant health.

Planting Sentinel European Trees in Eastern Asia as a Novel Method to Identify Potential Insect Pest Invaders

Quarantine measures to prevent insect invasions tend to focus on well-known pests but a large proportion of the recent invaders were not known to cause significant damage in their native range, or were not even known to science before their introduction. A novel method is proposed to detect new potential pests of woody plants in their region of origin before they are introduced to a new continent. Since Asia is currently considered to be the main supplier of insect invaders to Europe, sentinel trees were planted in China during 2007-2011 as an early warning tool to identify the potential for additional Asian insect species to colonize European trees. Seedlings (1-1.5 m tall) of five broadleaved (Quercus petraea, Q. suber, Q. ilex, Fagus sylvatica, and Carpinus betulus) and two conifer species (Abies alba and Cupressus sempervirens) were planted in blocks of 100 seedlings at two widely separated sites (one in a nursery near Beijing and the other in a forest environment near Fuyang in eastern China), and then regularly surveyed for colonization by insects. A total of 104 insect species, mostly defoliators, were observed on these new hosts, and at least six species were capable of larval development. Although a number of the insects observed were probably incidental feeders, 38 species had more than five colonization events, mostly infesting Q. petraea, and could be considered as being capable of switching to European trees if introduced to Europe. Three years was shown to be an appropriate duration for the experiment, since the rate of colonization then tended to plateau. A majority of the identified species appeared to have switched from agricultural crops and fruit trees rather than from forest trees. Although these results are promising, the method is not appropriate for xylophagous pests and other groups developing on larger trees. Apart from the logistical problems, the identification to species level of the specimens collected was a major difficulty. This situation could be improved by the development of molecular databases.

A Borer-Specific Assessment Scheme for Identifying Sentinel Trees to Delimit Invasive Borers in Urban Forests

Aggressive insects like the emerald ash borer [Agrilus planipennis (Fairmaire)] (EAB) increasingly threaten the health of the urban forest. Early detection of exotic wood-boring pests is critical for rapid response efforts, and allows for effective management while populations are relatively low. During street tree inventories, arborists record subjective rankings of tree condition and pest incidence; however, the extent of insect attack is rarely quantified. Moreover, it is unknown how the assessment of tree vigor provided by city foresters during these inventories relates to the likelihood of wood-borer infestation. In this study, researchers developed a borer-specific tree vigor assessment scheme to rapidly evaluate street trees, and to identify when EAB populations begin to grow exponentially based on the health of the forest. This scheme incorporates common indicators of EAB attack, including canopy thinning and epicormic sprouts, as well as attack by common native wood-boring insects. This scheme was used to track the health of ash trees from 2010 to 2013 in one urban forest with advanced symptoms of EAB decline and one without (Indianapolis and Lafayette, Indiana, U.S., respectively). Trees declined more rapidly in Indianapolis where emergence holes from native borers were positively correlated with EAB in infested areas. Over the course of the study, first detections of EAB occurred on progressively weaker trees at both sites, suggesting that early detection of incipient EAB populations can be improved by surveying apparently healthy trees.

Sentinel trees as a tool to forecast invasions of alien plant pathogens.

Recent disease outbreaks caused by alien invasive pathogens into European forests posed a serious threat to forest sustainability with relevant environmental and economic effects. Many of the alien tree pathogens recently introduced into Europe were not previously included on any quarantine lists, thus they were not subject to phytosanitary inspections. The identification and description of alien fungi potentially pathogenic to native European flora before their introduction in Europe, is a paramount need in order to limit the risk of invasion and the impact to forest ecosystems. To determine the potential invasive fungi, a sentinel trees plot was established in Fuyang, China, using healthy seedlings of European tree species including Quercus petreae, Q. suber, and Q. ilex. The fungal assemblage associated with symptomatic specimens was studied using the tag-encoded 454 pyrosequencing of the nuclear ribosomal internal transcribed spacer-1 (ITS 1). Taxa with probable Asiatic origin were identified and included plant pathogenic genera. These results indicate that sentinel plants may be a strategic tool to improve the prevention of bioinvasions.

Delimitation and management of emerald ash borer (Coleoptera: Buprestidae): case study at an outlier infestation in southwestern New York State, United States of America

AbstractWe present a case study in which we developed an adaptive delimitation technique and implemented and evaluated management of emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), in the first infestation discovered in New York State, United States of America. Delimitation was accomplished using 106 girdled “sentinel” trees and management included girdling 18 clusters of trees as population “sinks” to attract EAB and concentrate larvae for removal. Weekly monitoring of traps hung in sentinel trees facilitated early detection of EAB on 12 trees and allowed deployment of additional sentinels and sinks. Sentinel trees were felled and debarked; 12 were positive for EAB larvae and the spatial extent of infestation estimated at ∼48 km2. Sinks nearest the infestation core had the highest numbers of larvae. Larval densities were significantly greater in girdled trees than in proximate ungirdled trees suggesting removal of girdled trees prior to the following year's emergence would lower local EAB densities. Sinks deployed in response to an EAB on a sentinel tree purple prism trap more than 0.6 km from the centre of the known infestation were negative for EAB indicating these would not be effective for managing an infestation of similar size and in similar habitats. This case study provides valuable information to land managers to facilitate delimitation and management of newly discovered EAB infestations.

What's After Queer Theory? Queer Ethnic and Indigenous Studies

What's After Queer Theory? Queer Ethnic and IndigenousStudies Michael Hames-Garcia The decision to exercise intellectual sovereignty provides a crucial moment in the process from which resistance, hope, and most of all, imagination issue. —Robert Warrior, Tribal Secrets: Recovering American Indian Intellectual Traditions1 To what historical trajectory would queerness attach itself, so that it could be legible to itself and to others? Which geographic locations would be meaningful for queer theory's central inquiries? —Sharon Patricia Holland, The Erotic Life of Racism2 The Emergence of a Field Reading contemporary work in the field of what, for the pur poses of this essay, I will call queer ethnic and indigenous studies generally gives me a feeling of great satisfaction.3 In the works that comprise this still-emerging field, I see the fruition of conversations I remember taking place among queer graduate students of color in the 1990s. To be more precise, many of the conversations that I and many other graduate students (queer, of color, and queer of color) had during the 1990s—whether in the hallways of our graduate pro grams, or over drinks after watching the latest Spike Lee film, or FeministStudies39, no. 2. © 2013 by Michael Hames-Garcia 384 Michael Hames-Garcia 385 Books Discussed in This Essay Queer Indigenous Studies: Critical Interventions in Theory, Politics, and Literature. Edited by Qwo-Li Driskill, Chris Finley, Brian Joseph Gilley, and Scott Lauria Morgensen. Tucson: University of Arizona Press, 2011. The Erotic Life of Racism. By Sharon Patricia Holland. Durham, NC: Duke University Press, 2012. Strange Affinities: The Gender and Sexual Politics of Comparative Racialization. Edited by Grace Kyungwon Hong and Roderick A. Ferguson. Durham, NC: Duke University Press, 2011. Queer (Injustice: The Criminalization of LGBT People in the United States. By Joey L. Mogul, Andrea J. Ritchie, and Kay Whitlock. Boston: Beacon Press, 2012. sitting around someone's apartment living room on floor cushions discussing Kobena Mercer or Coco Fusco in a queer theory reading group, or while puzzling through a challenging passage by Jacques Lacan or Frantz Fanon in bed on a Sunday morning — have turned out to be the seeds from which the orchard of queer ethnic and indig enous studies has grown. In addition to the women of color and les bian of color feminisms that were already available to us in the 1980s and 1990s, the early sentinel trees in this forest appeared during the last decade of the millenium: including Kobena Mercer's 1994 Welcome to the Jungle: New Positions in Black Cultural Studies; Evelynn Hammonds's 1994 article "Black (W)holes and the Geometry of Black Female Sex uality" in differences; Kevin Mumford's 1997 Interzones: BlackjWhiteSex Dis tricts inChicagoandNew York intheEarlyTwentieth Century; Cathy Cohen's 1997 article "Punks, Bulldaggers, and Welfare Queens: The Radical Potential of Queer Politics?" in GLQ; David Eng and Alice Horn's 1998 collec tion Q & A: Queer inAsian America;José Esteban Muñoz's 1999 Disidenti fications:QueersofColorand thePerformance ofPolitics;and Emma Pérez's 1999 The Decolomal Imaginary: Writing Chicanas intoHistory}This trickle of books and articles transformed into a torrent in the following decade as the 386 Michael Hames-Garcia floodgates opened for scholars informed by the critical scholarship from ethnic studies, critical race theory, indigenous studies, queer theory, and feminism. Without wanting to suggest any absolute sepa ration among these fields, I would like to briefly tease out a few of the things that distinguish this emerging body of work from (1) women of color feminism and (2) queer theory, before going on to consider how the four texts under review here contribute to the field. It may be that the work of tracing continuities—particularly between this field and women of color feminism, as suggested by Grace Kyungwon Hong and Roderick A. Ferguson in their introduction to StrangeAffinities—is a generally more important project, but for the moment I am going to take the continuities for granted and see what can be learned from the discontinuities. In thinking about what distinguishes queer ethnic and indige nous studies from women of color and indigenous feminisms, the first,most obvious, answer lies in their relationship to queer theory. In other words, if women of...

Red mangrove (Rhizophora mangle) reproduction and seedling colonization after hurricane charley: Comparisons of Charlotte Harbor and Tampa Bay

Reproductive aspects of life history are known to be important in recovery following disturbance in many plant species although this has not been well studied in mangroves. Hurricane Charley devastated large areas of mangroves in Charlotte Harbor, Florida, in August 2004. We surveyed 6 forests in Charlotte Harbor (2002, 2003, and 2005) and 16 in Tampa Bay, Florida (2001, 2002, 2003, and 2005) for total numbers of reproducing trees and trees heterozygotic for albinism that produce both normal and albino propagules. Tree size (estimated height and diameter at breast height) was also recorded for sentinel heterozygotic trees. Total number of reproducing trees km−1 was used as an index of reproductive output of the population, and deviation from the 3∶1 (normal:albino propagules) ratio on heterozygotic trees expected with 100% selfing was used to estimate outcrossing. Numbers ofRhizophora mangle reproducing trees km−1 of shoreline in Charlotte Harbor were reduced by an order of magnitude following Hurricane Charley, while numbers of reproducing trees in Tampa Bay were similar to those of previous years. Reduced reproduction in Charlotte Harbor was accompanied by fewer new recruits in plots on Sanibel and Captiva Islands. Numbers of new recruits after the storm also tended to be fewer in plots where canopy loss was greater. More new recruits occurred in sites that had higher densities of pre-stormRhizophora seedlings and greater relative dominance byRhizophora. Outcrossing of sentinel trees was 2.5 times greater, in Charlotte Harbor (mean site−1=33.6±6.7%; with 17% of forest sites completely selfing) than in Tampa Bay (mean site−1=13.4±4.7%; with 40% of sites completely selfing), although the implications for seedling recruitment of this difference are not known.