Environmental Change - Abrupt

Question 1

Abrupt Changes

Answer 1

An abrupt change is a rapid shift from one state or condition to
another

ex: Forest Fire

Question 1

How does each type of change impact global
carbon cycle? (short-term)

Answer 1

Forest fire: Carbon transferred
to atmosphere

Forest regrows,
carbon transferred
back to forest

Forest harvest:
Carbon transferred to
forest products
(Houses, paper, etc.)

Forest regrows,
carbon transferred
back to forest

Land Cover/ land use change:
Can vary depending
on what happens to
the logs,

developing areas like houses and malls

Question 2

How does each type of change impact global
carbon cycle?(long-term)

Answer 2

Forest fire:
Forest regrows,
carbon transferred
back to forest

Forest harvest:
Forest regrows,
carbon transferred
back to forest

**Land cover/Land Use Change: **
Forest does NOT
regrow, carbon
NOT transferred
back to forest

Question 3

Changes also impact habitat in unique ways

Answer 3

• Fire is a natural part of ecosystems
• Recently burned areas can be important habitat for certain species

o Moose forage in recently burned areas
o Grizzly bears may prefer to forage in recently
burned areas

• Harvesting can alter ecosystems in unnatural ways
  o Can remove important habitat
• Land conversion from forest to agriculture or development leads to habitat loss

Question 4

Detecting Abrupt Changes

Answer 4

o First Step:we must detect where abrupt changes have occurred

o Second Step: , we must identify what type of disturbance it is

Question 4

How do we detect where abrupt changes have occurred?

Answer 4

We look for sharp changes in spectral signatures(NDVI)

Question 5

It is inefficient to look at entire spectral signatures

• To simplify, we can just focus on a metric like NDVI

Answer 5

Before fire
Green vegetation = High NDVI

After fire
Brown vegetation = Low NDVI

Question 6

we must identify what type of disturbance it is

Answer 6

• The shape and size of the
  disturbance

Fires and harvests have very
different shapes and sizes:

• Fires
  o Irregular perimeters
  o Large area
• Harvest
  o Regular shapes
  o Small area

Question 7

How can you differentiate between a forest harvest and land
conversion / land use change?

Answer 7

the key is in the pattern after the disturbence

harvest: forest regrows after a harvest(by law in BC)

Land is converted: forest does not regrow

Question 8

With satellite imagery we can:

Answer 8

• Detect fires
• Monitoring hotspots
• Monitor fire progression
• Calculate burned area
• Monitor vegetation recovery
• Data requirements for each of these?

Question 9

Hotspot Detection

Answer 9

Areas on the ground that are distinctly hotter than their surroundings

Thermal sensors measures the surface temperature and thermal properties of targets

• Early detection for coordination of forest fire fighting efforts

Instruments
* Landsat
* VIIRS
* MODIS

Question 10

Detecting Active FiresAll

Answer 10

active fires detected using MODIS

Question 11

Forest Harvest from Space

Answer 11

With satellite imagery we can:

• Detect forest harvest
• Calculate harvested area
• Monitor forest recovery

Data requirements?–

Question 12

Confirming Forest Harvest Amounts

Answer 12

• Government and industry make
  targets on forest harvest
• And create reports about on-the-
  ground harvesting
• Satellite data is an independent,
  standardized, objective dataset that
  allows us to confirm numbers from
  government/industry

Question 13

Land Cover vs. Land Use: Forest Harvest

Answer 13

Deforestation
* Forest is cut down
* Farms/plantations/communities
are developed

Land cover change:
* Forest to soil/vegetation/buildings

Land use change:
* Forestry to farm/plantation/community

Forest Harvest
* Forest is cut down
* Trees are planted and re-grown

Land cover change:
* Forest to bare ground initially,
then back to forest eventually

Land use change:
* Forestry to forestry (no change)

Question 14

Land Cover

Answer 14

Land cover is the physical and
biological cover over the
surface of land, including water,
vegetation, bare soil, and/or
artificial structures.

Question 15

Land use

Answer 15

is how we use land cover/ related to human activities such as agriculture,
forestry and urban construction
that alter land surface processes
including biogeochemistry,
hydrology and biodiversity.

Question 16

Land Cover(haverting) / Land Use Change

Answer 16

Often a change in land cover/land haversting could be temporary:
* Logging: land use does not change (managed forest)
* Forest -> bare soil
* Regrowth
* Bare soil -> shrubs -> forest

While a change in land use could be permanent/long-term:
* Residential development: land use changes from natural ecosystem to residential
area
* Forest -> concrete
* No regrowth

Land use vs. land cover change is an important distinction
* They each have different consequences(regrowth or no regrowth)

Question 17

What types of gradual trends do we see in forests?

Answer 17

• Slow mortality of trees due to insects or disease
• Gradual regrowth
• Reforestation
  o Transition from agriculture or developed land back to forests

Question 17

Gradual Changes

Answer 17

A gradual change is a slow shift
from one state or condition to
another, or a trend over time

Key Example:
o Rising sea surface
temperatures

Question 18

Mountain Pine Beetle

Answer 18

• Native insect to western North America

o Live in the bark of trees
* Although only 5mm in size, these insects have caused significant damage to
forests in BC

Question 19

Three stages of the attack(from the beetle)

Answer 19

o Green Attack – Adult beetles have tunneled under the bark. The tree begins to die, but the needles remain green

o Red Attack – After the tree has been dead for several months, the needles begin to turn red

o Grey Attack – The dead needles eventually fall, and a bare dead tree is left

Question 20

Why does an insect outbreak appear gradual from space?

Answer 20

The needles do not fall immediately when the tree dies

Not all trees die at the exact same time

o With Landsat, we are not measuring each tree individually!

Question 21

Gradual change in
spectral signature
as trees begin to
die (LANDSAT Pixel)

Answer 21

Healthy Trees =
High NDVI

Mix of healthy and
dead trees =
Slightly lower NDVI

Most trees are dead =
Low NDVI

Question 22

Gradual Change vs. Abrupt Change

Answer 22

insect outbreak (gradual) vs Fire(abrupt)

in a fire there is a suden dropp in NDVI but in an outbreak is little by little

Question 23

insect vs fire

Answer 23

While fire burns most trees, mountain pine beetle only attacks certain tree
species (mostly lodgepole pine).

o Therefore, the amount of damage will **depend on **what species of threes are in the
forest!

Question 24

What does a gradual disturbance followed by an abrupt disturbance(like harvesting) look like?

Answer 24

stady change(decrese) and then a sudden change/drop

Question 25

in the pine beetle (gradual)example the adrupt changes can be:

Answer 25

• salvage logs( just harvesting the wood in an attept to save some economic gain)
• forest fires as forests that are impacted by mountain pine beetle are also more likely to burn

Question 26

What other types of gradual changes in forests could we observe with satellite imagery?

Answer 26

• Mortality from disease and change in forest health
• As the climate changes, areas may become unsuitable for forests
  o Too hot, or not enough rain
• Therefore, we might notice slow changes from areas of forest to other land covers

Question 27

Why do we care about monitoring these
gradual losses of forests?

Answer 27

Although the changes are not abrupt, they can still have large impacts on carbon storage and habitat over time

Question 28

not all land conversions are abrup

Answer 28

We talked about land conversion as an abrupt change

o The conversion of forests to development
o The conversion of forests to agriculture

o Agriculture > Forest
o Developed land > Forest

ex:detroit

Question 29

Here are the changes in NDVI from 1975( to 2005
in Detroit derived from Landsat images

from abrupt to gradual

Answer 29

We see increases in NDVI across the city

Question 30

What do the results from Detroit tell us?

Answer 30

The changes we map using Landsat data are not always disturbances or habitat loss
* There is also forest gain

It is important to track the gradual recovery of forests if we want to paint a complete picture of how the planet is changing

Question 31

Review

Answer 31

Data requirements to detect change:
* Spatial detail
* Re-visit time
* Region of the EMS
* Temporal dimension

Types of change:
* Cyclical
o Vegetation phenology
* Abrupt
o Fires, forest harvest, land cover/land use change
* Gradual
o Insect infestation, forest recovery, land cover/land use change