Driving past a mass of tree stumps or seeing images of deforestation and its consequences for residing biodiversity can be an upsetting and unsettling sight. Land clearing is a major environmental issue faced globally and has many dire consequences; this is where remote sensing comes into play. Remote sensing images can be utilised to examine and monitor land clearing events at local, regional, national and even international scales.
For hundreds of thousands of years, people have cleared land for agricultural and development purposes. Now, we are really beginning to see the impact of this land clearing, deforestation and land use change, and it brings up an ethical dilemma that something must be done to prevent any more harm.
Like the famous words from the children’s book The Lorax which explores in its own way the issue of deforestation and land clearing:
“UNLESS someone like you cares a whole awful lot, nothing is going to get better. It’s not.”
– Dr. Seuss, The Lorax.
Remote sensing has allowed for us to make things better. It has provided the means to observe and monitor land clearing on a larger scale and over longer periods of time. Land clearing is a major environmental issue with a number of negative consequences. This makes remote sensing essential, in order to develop management plans to reduce land clearing.
Negative consequences of land clearing include:
- Habitat fragmentation (WWF n.d.).
- Clearance of native vegetation for introduced vegetation species (WWF n.d.).
- Removal of food and habitat for native species (ABS 2010).
- Increased salinity (ABS 2010).
- Increased invasion of weeds due to cleared land and open soil (ABS 2010).
- Soil degradation which can have flow on effects that negatively impact water quality of surrounding streams (ABS 2010).
Of most concern is the impact that land clearing will have on carbon emissions. Trees are a carbon storage, and clearance of land and removal of trees can release carbon into the atmosphere, increasing greenhouse gas emissions (WWF n.d.). Approximately 7% of Australia’s net emissions of carbon dioxide in 2009 was due to land clearing (Department of Climate Change and Energy Efficiency n.d. a).
This use of remote sensing in studying the impact land clearing and deforestation has on emissions can be seen in the Food and Agricultural Organisation of the United Nations video below.
Field work can also be used in conjunction with remote sensing data on land clearing and can help increase reliability of results (Ayanu et. al. 2015). However, it is remote sensing that as technology has improved, it has become possible for many industries to have a much broader area of scope.
In Australia, satellites, airborne sensors and ground-based platforms are used by state governments to map land clearing (Queensland Government 2013b) as well as any illegal land clearing that may be occurring on private properties (Queensland Government 2013a). The picture below shows land cleared between 1990 and 2009 in Australia. It is clear to see that a large portion of this occurred in Queensland.
Land clearing trends do suggest however that there is an overall decrease in the amount of land being cleared in Australia during 1990 and 2009 as evident in the graph below.
Depending on the scale of land clearing being mapped, spatial, temporal and spectral resolutions will vary. Spatial resolution will depend on the area of land being studied, temporal resolution can be low as land clearing and regrowth is a slow occurring event (Satellite Imaging Corporation 2015), and with spectral resolution, land clearing can be determined using near infrared bands on the electromagnetic spectrum (Centre for Remote Imaging, Sensing & Processing 2001).
Image subtraction is a useful transformation, or processing method of remote sensing data, for identifying deforestation and land clearing. It is used to identify changes between images. Spectral ratioing can also be useful in highlighting different spectral responses which allows for identification of different land cover types (Natural Resources Canada 2015a).
Land clearing should continue to be monitored and images should continue to be taken through remote sensors in order to observe land changes occurring globally over time. Unless rates of land clearing continue to decrease, biodiversity and species habitat are at risk of extinction, and carbon emissions will continue to climb, contributing to the global environmental issue of climate change.
Australia Bureau of Statistics 2010, 1370.0 – Measures of Australia’s Progress, 2010, Australian Government, viewed 20 May 2016, <http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/by%20Subject/1370.0~2010~Chapter~Land%20clearing%20%286.2.2%29>.
Ayanu, Y, Conrad, C, Jentsch, A & Koellner, T 2015, ‘Unveiling Undercover Cropland Inside Forests Using Landscape Variables: A Supplement to Remote Sensing Image Classification’, PLoS ONE, vol. 10, no. 6, e0130079.
Department of Climate Change and Energy Efficiency n.d. a, ‘Drivers of Land Clearing in Australia’, National Greenhouse Accounts Factsheet, Australian Government, viewed 20 May 2016, <http://www.environment.gov.au/system/files/pages/63b569ff-ae63-4d7b-be54-16f2e79900e0/files/nga-factsheet3.pdf>.
Department of Climate Change and Energy Efficiency n.d. b, ‘Land clearing – an assessment of biomass density’, National Greenhouse Accounts Factsheet, Australian Government, viewed 20 May 2016, <http://www.environment.gov.au/system/files/pages/63b569ff-ae63-4d7b-be54-16f2e79900e0/files/nga-factsheet4.pdf>
Natural Resources Canada 2015a, Image Transformations, Government of Canada, viewed 20 May 2016, <http://www.nrcan.gc.ca/earth-sciences/geomatics/satellite-imagery-air-photos/satellite-imagery-products/educational-resources/9377>.
Queensland Government 2013a, Assessing land clearing, Queensland Government, Australia, viewed 20 May 2016, <https://www.qld.gov.au/environment/land/vegetation/mapping/land-clearing/>.
Queensland Government 2013b, Remote sensing centre, Queensland Government, Australia, viewed 20 May 2016, <https://www.qld.gov.au/environment/land/vegetation/mapping/remote-sensing/>. Satellite Imaging Corporation 2015),
Satellite Imaging Corporation 2015, Satellite Remote Sensing Systems, Satellite Imaging Corporation, United States, viewed 20 May 2016 <http://www.satimagingcorp.com/services/resources/characterization-of-satellite-remote-sensing-systems/>.
WWF n.d., Landclearing, World Wildlife Fund, Australia, viewed 20 May 2016, <http://www.wwf.org.au/news_resources/archives/landclearing/>.