Environmental Monitoring Commons^™

Land Condition Standards For The Western Australian Nullarbor Pastoral Region, Peter-Jon A. Waddell, Wayne J. Fletcher

Natural resources published reports

This report outlines the quantitative land condition standards that define acceptable pastoral land condition for the Western Australian part of the Nullarbor, to meet the regulatory requirements of the Land Administration Act 1997 and the Soil and Land Conservation Act 1945.

The Department of Primary Industries and Regional Development is developing regional-level pastoral land condition standards for Western Australia as a critical component of the Framework for sustainable pastoral management – revised edition (Fletcher 2022), the purpose of which is to address the Office of the Auditor General’s recommendations to improve the management of pastoral lands in WA …

Harmful Algal Blooms: Risks For Food In Utah, Jose Brandao, Sarah Erwin, Stephanie Vaughn, Clare Entwistle

All Current Publications

Harmful algal blooms (HABs) are a problem because they can produce toxins that make water unsafe for people, animals, and the environment. In recent years, HABs have emerged as a growing concern in freshwater systems throughout Utah, including irrigation canals, reservoirs, and livestock ponds. HABs in freshwater are caused by cyanobacteria, also called blue-green algae. These microorganisms can release dangerous toxins that can harm swimmers, pets, and the food supply. Unlike foodborne pathogens, these toxins cannot be removed by boiling, cooking, or washing the food. Therefore, regular monitoring is essential to detect HABs early and reduce exposure risks. This fact …

Long-Term Variability Of Air Quality And Greenhouse Gas Emissions From Rice Crop Burning In Punjab During 2012–2020, Harsimranjit Kaur Romana, Dericks Praise Shukla, Ramesh P. Singh

Mathematics, Physics, and Computer Science Faculty Articles and Research

Punjab, India's primary rice and wheat production hub, has witnessed rapid expansion of paddy cultivation over the past two decades, driven by minimum support price incentives, changes in government policies, alignment of sowing with the monsoon season and the adoption of high-yielding varieties. This transition has intensified groundwater extraction and shortened the fallow period between rabi and kharif crop seasons, reducing the window between rice harvesting and wheat sowing, leading to widespread open-field burning of rice residue and recurrent post-monsoon air-quality deterioration across the Indo-Gangetic Plain. Despite numerous short-term or single-pollutant assessments, a spatially resolved, multi-pollutant and multi-decadal evaluation linking …

To Hold Or Sell Breeding Cattle In The Rangelands, Department Of Primary Industries And Regional Development, Western Australia

Animal production and livestock factsheets

In a dry season where feed, water and finances are limited, removing less productive animals as soon as possible is a good option. This will free up feed for more productive animals and help preserve ground cover.

This page provides some of the information and a process for making decisions about holding or selling breeding cattle.

Status Of The Western Australian Pastoral Rangelands 2025 - Total Vegetative Cover And Cover Risk, Department Of Primary Industries And Regional Development, Western Australia

Natural resources published reports

DPIRD monitors and reports on the vegetation condition of pastoral rangelands in Western Australia. Two levels of reporting are provided: every 5 years a full report details the state, trend and risk of decrease of vegetation condition in the pastoral rangelands using information derived from remotely sensed and on-ground data; in the intervening years, short reports are provided based on remotely sensed data (this report).

This report is based on remotely sensed vegetation cover data, rainfall data, livestock data and station-level rangeland condition assessment (RCA) data available in November 2025. Data is presented for 23 land conservation districts (LCDs) across …

High Spatiotemporal Resolution Monitoring Of Crop Water Stress Across The Contiguous United States Using Harmonized Landsat And Sentinel-2 Data, Na Chen, Yanlei Feng, Na Wang, Jevan Yu, Mohammad Reza Alizadeh, Yifeng Cui, Ning Ye, Wenzhe Jiao, Joshua B. Fisher, César Terrer

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Accurate and timely monitoring of crop water stress is essential for efficient agricultural water management, ultimately maintaining and improving crop productivity. While Landsat has been used for this purpose, its temporal resolution hampers timely detection of crop water stress. The recently released Harmonized Landsat and Sentinel-2 Version 2.0 dataset, which enables a higher-frequency time series of satellite observations (2–3 days, 30 m), offers a promising solution to this challenge. However, its potential for crop stress monitoring remained unexplored. In this study, we utilized 923 HLS satellite tiles to assess crop water stress across the contiguous United States (CONUS). Crop water …

Neonicotinoid Bioaccumulation In Bluegill And Bullhead Within Lake Julia And Lake Zumwalde, Jake Stuber

Journal of Earth and Life Science

Brown Bullhead Ameiurus nebulosus, Yellow Bullhead Ameiurus natalis, and Bluegill Lepomis macrochirus are unique in their stark differences. Bullhead are scaleless bottom feeders that can tolerate high pollution and low O₂ conditions. In contrast, Bluegill are scaled, aggressive nesters and are less tolerant of high pollutants or low-oxygen conditions. Among these pollutants include a class of chemicals called neonicotinoids (hereafter referred to as neonics). Neonics are a class of insecticides primarily used within agriculture and pest management. Due to the effectiveness, application has escalated on a global scale. They have been well documented by many toxicology assessments. …

Quantifying Single, Compound And Cascading Climate Extremes: Implications For Agricultural Resilience In California, Shahryar Fazli, Wenzhao Li, Rejoice Thomas, Surendra Maharjan, Mohammad Sina Jahangiri, Andre Daccache, Hesham Morgan, Mohamed Allali, Hesham El-Askary

Mathematics, Physics, and Computer Science Faculty Articles and Research

As climate change intensifies, extreme weather increasingly threatens California’s Central Valley (CV), a vital agricultural region exposed to rising risks from heatwaves (HW), droughts (DR), and compound extremes. These events disrupt crop productivity and broader processes like water demand, pest dynamics, and soil stability, posing systemic risks. This study examines the spatiotemporal dynamics of HW, coldwaves (CW), DR, excessive rainfall (ER), and their compound (e.g., HWDR) and cascading forms from 1951 to 2025, using NOAA nClimGrid-Daily data. We assessed trends in frequency, intensity, and duration over long-term (1951–2025) and mid-term (1981–2025) periods. Results show increasing HW and DR in the …

A Feature Engineering Technique For Enhancing The Generalization Of Machine Learning Models In Estimating Crop Evapotranspiration, Gaku Yokoyama, Sohta Harigai, Shigehiro Kubota, Koichi Nomura, Gregory R. Goldsmith, Daisuke Yasutake, Tomoyoshi Hirota, Masaharu Kitano

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Accurate and precise estimation of evapotranspiration (ET) is crucial for understanding the terrestrial carbon, water, and energy cycles. While process-based models of ET, such as the Penman–Monteith model offer robust generalization capabilities, they are limited by the need for detailed parameters (e.g., stomatal conductance,) that are challenging to measure continuously. On the other hand, machine learning models can estimate ET by capturing relationships between ET and environmental variables without experimentally measuring model parameters. However, machine learning models face the challenge of limited generalizability. This issue is particularly significant given the uncertainty introduced by changing climatic …

Unraveling Crop Nitrogen-Water Dynamics With Hyperspectral-Thermal Sensing In Northern Central Valley, California, Shahryar Fazli, Surendra Maharjan, Wenzhao Li, Joshua B. Fisher, Rejoice Thomas, Fernando Romero Galvan, Gabriela Shirkey, Hesham El-Askary

Mathematics, Physics, and Computer Science Faculty Articles and Research

Ensuring global food security in the face of climate change requires optimizing crop water use and nutrient management. This study investigates the relationship between canopy nitrogen (N) and evapotranspiration (ET) across sunflower, rice, walnut, alfalfa, and plum crops using advanced remote sensing technologies. High-resolution hyperspectral data from NASAs Earth Surface Mineral Dust Source Investigation (EMIT) and thermal multispectral data from the Landsat-based OpenET system were analyzed over 1,135 km² in California. Regression analysis revealed strong spatial association between canopy N and ET for sunflower (R² = 0.82), rice (R² = 0.71), and walnut (R² = 0.68), …

Procedures For Rangeland Condition Assessment In The Pilbara And Southern Rangelands 2025, Department Of Primary Industries And Regional Development, Western Australia

Natural resources published reports

This report defines the procedures used in 2025 by DPIRD to complete rangeland condition assessment (RCA) in the Pilbara and southern rangelands region which has predominantly shrub-based pastures. For the rest of the pastoral estate, DPIRD uses the Procedures for RCA in the Kimberley which has grass pastures.

RCA is the process DPIRD uses to make systematic, station-level assessment of rangeland. Rangeland condition considers both the condition of pastures (defined in the ‘Pasture condition guides for the Pilbara’ and ‘Pasture condition guides for the southern rangelands including the Gascoyne, Murchison and Goldfields-Nullarbor’) and soils as determined by erosion, using the …

Procedures For Rangeland Condition Assessment In The Kimberley 2025, Department Of Primary Industries And Regional Development, Western Australia

Natural resources published reports

This report defines the procedures used in 2025 by DPIRD to complete rangeland condition assessment (RCA) in the Kimberley region which has grass-based pastures. For the rest of the pastoral estate, DPIRD uses the Procedures for RCA in the Pilbara and southern rangelands which have predominantly shrub pastures.

RCA is the process DPIRD uses to make systematic, station-level assessment of rangeland. Rangeland condition considers both the condition of pastures (as defined in the 'Pasture condition guide for the Kimberley') and soils as determined by erosion, using the erosion assessment method on pastoral lands in Western Australia. The methods have evolved …

Multi-Crop Systems And Crop-Switching Strategies To Enhance Water Use Efficiency And Climate Resilience In Arid Agricultural Regions, Shahryar Fazli, Wenzhao Li, Surendra Maharjan, Hesham El-Askary

Mathematics, Physics, and Computer Science Faculty Articles and Research

Agriculture in the Lower Colorado River (LCR) region faces mounting challenges from climate change, arid conditions, and water scarcity. This study evaluates water use efficiency (WUEc) and crop-switching strategies under SSP2-4.5 and SSP5-8.5 scenarios for 2025–2049, 2050–2074, and 2075–2099. Using historical data, climatic drivers such as temperature and precipitation were analyzed for their influence on key crops, including durum wheat, winter wheat, and corn. Results show SSP2-4.5 supports water use reductions up to 16%, stable profits (80–90%), and modest calorie increases (up to 15%), while SSP5-8.5 poses severe challenges, with water use reductions of 2–5%, profits dropping to around 20%, …

Adaptive Crop Switching For Irrigated Agriculture In Response To Climate Change In The Western U.S., Shahryar Fazli, Wenzhao Li, Surendra Maharjan, Rejoice Thomas, Aqil Tariq, Hesham El-Askary

Mathematics, Physics, and Computer Science Faculty Articles and Research

Adaptive irrigation strategies are crucial for balancing water use, economic viability, and food security in the arid Western United States. However, as a key indicator vital in regulating agricultural productivity and crop irrigation, water use efficiency (WUEc) is becoming increasingly complex to estimate due to climate change. This study explores the critical role of key meteorological drivers, such as maximum temperature (tmax) and vapor pressure deficit (vpd), and their impacts on crop-specific WUEc. Future impacts are also assessed through integrating machine learning models with climate projections from the CMIP6 framework under SSP2–4.5 and SSP5–8.5 scenarios to forecast WUEc trends from …

High Spatial Resolution Crop Type And Land Use Land Cover Classification Without Labels: A Framework Using Multi-Temporal Planetscope Images And Variational Bayesian Gaussian Mixture Model, Minh Tri Le

Mathematics, Physics, and Computer Science Faculty Articles and Research

Previous studies often combined high spatial resolution data (e.g., PlanetScope) with wider spectral range data (e.g., Sentinel-2) and relied on supervised classification methods to produce land use and land cover (LULC) maps. This study proposed a new unsupervised framework to generate crop type and LULC maps at high spatial resolution (< 5 m) using available PlanetScope data solely without requiring ground truths. We used PlanetScope surface reflectance images and their derived spectral indices during growing seasons to create multi-temporal input features, which were fed into an unsupervised Variational Bayesian Gaussian Mixture Model (VBGMM). The VBGMM, unlike the traditional unsupervised classification methods, (1) first estimated optimal parameters that are most suitable based on the input features and then (2) assigned pixels to the cluster with maximum posteriori probability of a mixture of several Gaussian distributions. The crop type and LULC maps were then generated by labeling the derived clusters using the best possible assignment method, referring to the existing crop type or LULC products. We evaluated the produced PlanetScope-based crop type and LULC maps using true labels, corresponding reference maps, and other unsupervised classification methods. The results demonstrated the robustness and effectiveness of the proposed framework in mapping crop types and LULC at 3–5 m pixels across various ecosystems, climate zones, and human-managed landscapes. The spatial patterns of PlanetScope-based maps were (1) highly comparable with all the reference datasets at 10–30 m spatial resolution and (2) better than the traditional GMM and K-means clustering methods. The VBGMM produced classification maps with high confidence, yielding class probabilities above 0.9 for over 90 % of all study areas. The area percentage for all crop type and LULC classes agreed well with their reference maps, with R2 of 0.95 and RMSE of 1.04 %. The confusion matrices using true labels indicated that PlanetScope-based maps achieved a higher overall accuracy of 84 % than the supervised referenced maps of 81 %. Besides, the entropy comparison showed that our framework-based maps were better at capturing fine-scale features such as developed areas within cities that commonly mix with open space and vegetation, deforestation and cropland conversion in South America, smallholder croplands in Africa and Asia, and generating homogeneous crop fields in North America. This study further highlighted the potential for future research to implement our proposed framework to generate timely and extensive annotated datasets, which can be used for operationally training machine learning models to map crop types and LULC, track deforestation, detect wildfires, and delineate flooded areas at larger scales using medium/coarse Earth observations.

Status Of The Western Australian Pastoral Rangelands 2024: Total Vegetative Cover, Cover Risk And Pasture Condition, Department Of Primary Industries And Regional Development, Western Australia

Natural resources published reports

The Department of Primary Industries and Regional Development (DPIRD) monitors and reports on the vegetation condition of pastoral rangelands in Western Australia. Two levels of reporting are provided: every 5 years a full report (this report) details the state, trend and risk of decrease of vegetation condition in the pastoral rangelands using information derived from remotely sensed and on-ground data; in the intervening years, short reports are provided based on remotely sensed data.

This full report is based on remotely sensed vegetation cover data, rainfall data, livestock data and station-level rangeland condition assessment (RCA) data available in November 2024. Data …

Enhancing Water Scarcity Resilience In Egypt Through Machine Learning-Driven Phenological Crop Mapping And Water Use Efficiency Analysis, Surendra Maharjan, Wenzhao Li, Shahryar Fazli, Aqil Tariq, Rejoice Thomas, Cyril Rakovski, Hesham El-Askary

Mathematics, Physics, and Computer Science Faculty Articles and Research

Agriculture forms the backbone of Egypt’s economy, with the Nile Valley and Delta serving as key production zones for crops like wheat, rice, and clover. However, the sector faces mounting pressure from water scarcity, as it depends almost entirely on the Nile for irrigation, making it necessary to map major crops for assessing Water Use Efficiency (WUE) and informing agricultural planning. In this study, we used machine learning (ML) techniques—specifically Support Vector Machine (SVM) to time-series phenological data and optical indices (Enhanced Vegetation Index (EVI), Bare Soil Index (BSI), Land Surface Water Index (LSWI), Normalized Difference Vegetation Index (NDVI), and …

State And Transition Models For Mulga Rangelands Of Western Australia, Alison O'Donnell, Anna E. Richards, Suzanne Prober, Peter-Jon A. Waddell, Sarah Luxton, Ian Watson, Brett Abbott, Philip Thomas, Joshua E. Foster

Natural resources published reports

This report details a collaborative project between the Western Australian Department of Primary Industries and Regional Development and CSIRO that focused on developing State and Transition Models (STMs) for mulga rangelands in Western Australia. The overarching aim of the project was to improve the common understanding of the characteristics and dynamics of mulga rangeland ecosystems and the expected impacts of management. Specifically, the project aimed to collate expert knowledge and monitoring information using a nationally consistent framework to develop quantitative and dynamic STMs. The geographic scope of the project covers the extensive mulga rangelands of Western Australia, particularly the Gascoyne …

Pastoral Land Condition: Kimberley Land Condition Standards, Robert Sudmeyer, Rick Fletcher, Kathryn Ryan, Matthew Fletcher, Charles Martin, Philip Thomas, Karen Holmes, Karyn Reeves, Wayne Fletcher

Natural resources published reports

This report outlines the conceptual basis and quantitative land condition standards that define acceptable pastoral land condition for the Kimberley, Western Australia (WA), to meet the regulatory requirements of the Land Administration Act 1997 and the Soil and Land Conservation Act 1945.

The Department of Primary Industries and Regional Development (DPIRD) develops regional-level pastoral land condition standards for WA to implement the Framework for sustainable pastoral management – Revised edition, which is designed to address the Office of the Auditor General’s recommendations to improve the management of pastoral lands in WA. The application of these standards is expected to …

Modeling Wild Rice Bed Health: A Dual Metric Approach For Bed Strength And Invasive Impact, Seth Sisneros-Martinez

Journal of Earth and Life Science

Wild rice (mannoomin; Zizania palustris) is an aquatic grain that grows in slow-moving rivers and shallow bays throughout northern Minnesota. In Headquarters Bay on Leech Lake, wild rice has served as a cultural staple for Indigenous communities for centuries. However, its population has declined in recent years due to multiple environmental issues. One potential contributor is Eurasian watermilfoil (Myriophyllum spicatum; EWM), an invasive species that forms dense mats capable of outcompeting native aquatic vegetation, including wild rice. EWM was first recorded on the southern shoreline of Leech Lake in 2005 and has since become widespread. This study …

Identifying Intangible And Biocultural Heritage Elements Toward Environmental Understanding: Engaging Stakeholders Through Art, Martha B. Lerski

Publications and Research

Grounded in a case study in Barbuda in the Caribbean, this research examines sustainability from the perspective of what arts and heritage can contribute to community engagement and local and broader understandings about the environment. This article documents a growing body of literature recognizing the role of arts and culture, including local knowledge and traditional ecological knowledge (TEK), in climate change endeavors. Art and TEK present expansive world views. Contextual information situates research done on the island of Barbuda pre- and post-Hurricane Irma. Visual arts workshops engaged community members in mixed methods research. Results documented cultural elements, particularly intangible and …

Farm Profit Impacts Of Consecutive Drought Years Under Climate Scenarios In Southwestern Australia, Sud Kharel, Kevin J. Foster, Meredith M. Guthrie, Ross Kingwell

Climate Science Research Articles

Climate projections for southern Australia indicate an increased likelihood of years of consecutive droughts. How resilient are farm businesses and their farming systems to recover from episodic drought? This study assesses the farm economic and financial impacts of consecutive droughts in southwest Australia. Bioeconomic simulation modelling of farm businesses with different farming systems at three locations is used to examine the long-term financial consequences of consecutive droughts. Various key factors affecting those consequences are examined. Farm location, farming system and starting equity are found to be the main determinants of how quickly a farm business can financially recover from the …

Estimating The Carbon Footprint Of Sheep Production In Western Australia, Tafesse Estifanos, Christophe D'Abbadie, Johnny Machon, Amir Abadi Abadi Ghadim, Gus Manatsa, Paul Mattingley, Ross Kingwell, Kevin Foster

Farm Systems and Economics published reports

Western Australia’s broadacre mixed farming systems combine cropping and sheep production and are the largest component of the state’s agricultural sector. The south west Western Australia (WA) agricultural area hosts about 98% of the state's sheep flock. The sheep industry contributed $1.5 billion to the state’s economy in 2021-22 and accounts for about a quarter of on-farm greenhouse gas (GHG) emissions. Most sheep industry emissions (over 80%) come from methane produced by the sheep. Despite this environmental impact, only 9.9% of Australian sheep producers have estimated their emissions, which limits the industry's ability to monitor and manage carbon footprints effectively. …

Multi-Sensor Data Fusion And Gis-Drastic Integration For Groundwater Vulnerability Assessment With Rainfall Consideration, Wu Jiazhe, Dai Xinrui, Su Yangcheng, Zheng Xiangtian, Bushra Ghaffar, Rabiya Nasir, Ahsan Jamil, Zeeshan Zafar, Mohammad Suhail Meer, M. Abdullah-Al-Wadud, Rahila Naseer, Hesham El-Askary

Mathematics, Physics, and Computer Science Faculty Articles and Research

In many areas of the world, particularly in arid and semi-arid regions, groundwater is the primary source of fresh water, and it supplies around one-third of the world's fresh water. Agriculture is the primary economic sector on the coast in the southern district (Nowshera). More food productivity is required due to the expanding population and diminishing agricultural lands, which increases the use of chemical pesticides and fertilizers in farming. The current study was conducted in northwestern parts of Pakistan to evaluate the impacts of the frequent use of pesticides and fertilizers in agricultural fields. Nine hydrogeological parameters were considered, and …

Identifying Opportunities For Nature-Based Solutions With Geospatialized Life Cycle Assessments And Fine-Scale Socioecological Data, Gabriela Shirkey, Annick Anctil, Ranjeet John, Venkatesh Kolluru, Leah Mungai, Herve Kashongwe, Lauren T. Cooper, Ilke Celik, Joshua B. Fisher, Jiquan Chen

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

As we increasingly understand the impact that land management intensification has on local and global climate, the call for nature-based solutions (NbS) in agroecosystems has expanded. Moreover, the pressing need to determine when and where NbS should be used raises challenges to socioecological data integration as we overcome spatiotemporal resolutions. Natural and working lands is an effort promoting NbS, particularly emissions reduction and carbon stock maintenance in forests. To overcome the spatiotemporal limitation, we integrated life cycle assessments (LCA), an ecological carbon stock model, and a land cover land use change model to synthesize rates of global warming potential (GWP) …

Western Australian Soil Groups - A Diagnostic Key To Identify Soils In Western Australia (5th Edition), Paul Galloway, Dennis Van Gool, Angela Stuart-Street, Edward A. Griffin, Shahab Pathan, Noel R. Schoknecht

Resource management technical reports

The aim of the Western Australian soil groups (WA soil groups) is to classify soils of Western Australia into a limited set using criteria that are easy to recognise in the field. It is a general-purpose classification with a focus on agronomic and rangeland grazing potential. The WA soil groups are designed for WA needs. It complements the Australian Soil Classification (ASC) by grouping the continuum of soils into a limited set of soil types, which simplifies soil variability for generalists, allows soil surveyors to create standardised soil-type legends for mapping products and permits further analyses of spatial data for …

Leveraging High-Frequency Water Quality Data And Machine Learning For Monitoring Harmful Algal Blooms, Ibrahim Busari

All Dissertations

Freshwater management is one of the most critical resources on the earth due to the plethora of water use and its limited availability. Increased algae proliferation is one of the significant problems of freshwater bodies that is triggered by nutrient enrichment and enabling conditions such as light and warm temperatures. This algal proliferation is toxic to the ecosystem through their biomass and potential toxin production that can cause hypoxic conditions and is often referred to as Harmful Algal Blooms (HABs). Current monitoring approaches include laboratory analysis of water samples to observe algal cells, monitoring of water quality parameters using water …

Evaporation Basins For Salinity Management, Department Of Primary Industries And Regional Development, Western Australia

Natural resources factsheets

An evaporation basin is an engineered earth structure designed to safely store and evaporate saline water discharged from drainage or pumping, while protecting high-value agricultural land, natural assets or built infrastructure.

DPIRD recommends that evaporation basins should form part of an integrated water and salinity management program. Information on this page is a guide only.

It is recommended that landholders seek expert advice plus engineering design and related support from qualified contractors.

Rabbit Control: Bait Products, Department Of Primary Industries And Regional Development, Western Australia

Biosecurity factsheets

This factsheet is part of the bait and poison directory for vertebrate pests in Western Australia (WA). It provides information on bait, poison, and toxin (bait) products available for use in WA to control rabbits (Oryctolagus cuniculus).

For information on how to access bait, poison and toxin (bait) products, training required, animal welfare considerations and legal requirements, refer to the Bait and poison directory for vertebrate pests’ page on the website at dpird.wa.gov.au. Information on bait, poison, and toxin (bait) products available for use in WA for rabbits, is provided below.

Bathurst Burr And Its Control, Department Of Primary Industries And Regional Development, Western Australia

Biosecurity factsheets

Bathurst burr (Xanthium spinosum) is a declared pest in Western Australia (WA). This factsheet describes the nature of the plant, requirements land owners/occupiers must adhere to, control methods, and how to search, detect, and report it.

Bathurst burr is a summer growing annual shrubby plant originating in South America. In south west Australia, some mature plants survive well into winter, with the result that burrs may be found for most of the year. The weed spreads entirely by burrs, which are usually carried by people or animals, attached to clothes, fur, or other fibre by their hooked spines. They may …