Earth’s land surfaces form an ever-changing patchwork
of land cover types: desert, tundra, pastureland, forest,
swamp, etc. As our uses of them change, so too do the land
types themselves. As boreal forests in North America give
way to human development, so too do rain forests in South
America, savannahs in Africa, and deserts in Asia. With the
climate changing, worldwide resources dwindling, and human
populations dramatically swelling, keeping track of those
different land types is becoming more and more important.
To help meet this need, MODIS scientists developed the Land
Cover Type / Land Cover Change product (MOD 12).
Just 100 years ago, there were only 1.7 billion humans on
Earth. Today the total stands at over 6 billion, and by the
year 2025, that number is expected to increase by almost two
billion. Keeping all those people fed and housed is a problem
that every nation faces, but the problem is especially critical
to those nations where resources are scarce and populations
high (like Japan). Thus, keeping track of those resources
that are available and how they are changing in response to
human development and climate change is important.
Conservation efforts are also dependant upon and sensitive
to changes in and amounts of different types of land cover.
Many species’ natural habitats are shrinking at an alarming
rate, and many habitats have completely disappeared. Conservation
and rehabilitation efforts rely heavily on knowing where and
how much of suitable land cover types exist. Wolves are one
of a number of species undergoing a habitat rehabilitation
effort, particularly in North America, where most of the wolf
population was systematically exterminated in the last two
centuries. Now that they are a protected species, there are
many programs underway to increase their numbers and find
land suitable for their reintroduction: mostly forest with
little or no urban or farmland areas, covering anywhere from
20 to 120 square miles per pack. Many research and conservation
programs use remotely sensed land-cover observations to identify
Public health also depends on accurate land cover data. The
West Nile Virus and Malaria, both of which are spread by mosquitoes,
are linked to certain types of land cover, such as swamps.
Public health officials can use the data provided in the MODIS
Land Cover product to identify areas where they should concentrate
their efforts to fight spread of these maladies. Land cover
type and change have also been linked to water quality. As
humans change land to suit their needs – like using
former grasslands as farmland and cutting down forests to
free up land for livestock grazing – these changes can
introduce or contribute to contaminants in the water supply.
The use of pesticides in farming often contributes to declining
water quality, and can persist for decades. By observing how
land cover types change, public health officials can predict
how water quality might change as well.
Perhaps the most important aspect of land cover data is its
continuity. Land cover type can be determined in a relatively
short period of time, but such static data will have a limited
shelf life. By monitoring land cover type over an extended
period of time, the observations will show how land cover
types subtly and progressively change under environmental
and human pressures. MODIS’ Land Cover Type / Land Cover
Change product not only documents change over a period of
time, but can determine both the type of change and its intensity.
Because changes in land cover can vary in intensity over a
given period of time, this attribute of the data set is quite
Because the planet’s land resources are limited, keeping
track of them as we increasingly make use of and change them
becomes more and more important, both locally and globally.
Disappearing and changing land-types cost us more than just
the land-types themselves; we also loose valuable resources
that are difficult – if not impossible – to replace.
As deforestation occurs, fewer forest products are available.
Lumber is an obvious resource, but deforestation also deprives
us of as-yet-undiscovered resources, especially in the tropical
rainforests of Asia and South America.
Desertification ruins grazing land and thus leaves less room
and food for livestock, which are integral to many country’s
economies. As urbanization consumes farmland, farms are forced
to move farther and farther away from the populace that requires
the food, oftentimes making the food more expensive and causing
the degradation of native land types. In particular, converting
deserts and savannahs to farmland has a significant impact
on local sources of fresh water: depletion and pollution are
major issues that must be dealt with.
The Land Cover Type / Land Cover Change product, and continuous
data sets like it, will and continue to help scientists to
gain a broader and deeper understanding of the these issues,
the planet, and ourselves. This will in turn benefit conservation
and planning efforts, which will ultimately be to the benefit
of present and future generations.