Selected Sites for Land Cover Changes
Sites were selected from each country to provide examples
of the change detection and land cover results (Figure 2). In
2006 a reservoir for a hydroelectric project was developed
in northern Quebec. This change from largely lower density
conifer forest to water was well captured and is marked as A
in Figure 2-I. Several large fires are also evident surrounding
the reservoir. Fires that occurred in 2004-2005 (B) can be
seen as regeneration from temperate or sub-polar grassland
to temperate or sub-polar shrubland. A small burn that
occurred in 2008 (C) is shown to the west of the main body of
the reservoir. An area that has undergone repeated burning
is marked as D. In 2010 the reservoir water level was very
low, which is the cause for the spatial disagreement between
the 2010 land cover and MODIS imagery. As this was a single
year occurrence, it was not captured in the change product
as only persistence water changes were accepted as change.
In 2007 several large forest fires burned extensive forested
areas in central Idaho, and several of these very large
patches are represented here for the Payette National Forest
for which the burnt area (1,905km
2
) was eight-times higher
than the 20-year average (Tily, 2008). The entire western
zone (A-C) of Figure 2-II shows lightning-ignited wildland
fires that burned into each other. For instance, the Zena-
Loon fire (B), that consumed 871km
2
of mostly forested area,
formed by different lightning strikes in early to mid-July
and later combined with the Raines fire (C; 317km
2
) and the
Monument/Riordan fire (A) which extends even further to
the South. The July image and classification of 2010 show
recovering vegetation as Temperate or sub-polar grassland
and early successional stages of Temperate or sub-polar
shrubland.
The city of Merida on the Yucatan Peninsula depicts notable
urban growth between 2005 and 2010. Although once the city
limits were established by the outer city ring (Periférico),
which largely coincides with the extent of urban area of
2005, Merida grew beyond those boundaries over the 5-year
period. For instance, the Fraccionamiento Las Américas (A in
Figure 2-III; 225ha in 2010) was constructed for an expected
population of 20,000 habitants. The largest new city section,
Ciudad Caucel (B; 875 ha in 2010), is designed for 30,000 new
houses and an expected population of 100,000 new residents.
There are other growing urban sections adjacent to the city
such as Villas de Oriente (C; 162.5 ha).
C
onclusions
and
F
uture
P
roducts
The completion of an updated 2010 North American land
cover product, with the accompanying land cover change
from 2005 provides important continental-scale information
for a variety of potential applications. Main steps in this
process were: 1) the improvement of the NALCMS base line
land cover map for 2005, 2) the development of the change
product between the years 2005 and 2010, and 3) labeling the
change to complete a 2010 land cover map. These products
were initially developed by the NALCMS working group
to test the feasibility of change detection approaches for
potential future processing of annual land cover time series.
It was recognized that these products would serve various
national and international user communities seeking to
draw conclusions from changes over a 5-year interval. This
approach also highlights the limitations of change detection
at moderate spatial resolution for smaller, more complex
land cover ensembles and indicates areas for improvement,
e.g. the reduction of the commission error for potential
change in Mexico. Nevertheless, MODIS image time series
have distinct advantages over other data sources as daily
image acquisition increases the probability for cloud-free
observations at various stages of vegetation growth, as an
additional information for change detection algorithms.
Future work is now underway to produce annual 250 m land
cover change products for North America, with additional
work exploring the feasibility of products being offered at the
30 m scale.
All land cover maps and change products can be downloaded
for the entire continent from
and for
individual countries from institutional websites, e.g. United
States:
and Mexico
.
conabio.gob.mx/informacion/gis/.
Future work is now underway to produce
annual 250 m land cover change products for
North America, with additional work exploring
the feasibility of products being offered at the
30 m scale.
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
October 2014
923
