Environmental Change: Cycle in vegetation Flashcards
Earth is Constantly Changing
- Natural change
- Human caused change
- Change occurs on various scales
- Time
- Wildfires burn over days & weeks
- Climate change occurs over decades & centuries
- Space
- Wildfires burn over 0.1 – 10km2
- Climate change occurs across the globe
Monitoring Environmental Change
Valuable for a variety of reasons:
- Minimize impact on environment
- Ensure compliance with laws
- Protect human health
- Predicting into the future
Why would satellite data be advantageous for monitoring environmental change from space?
- standerlized data, efficency,
Data Requirements
- Data requirements vary with the type of environmental change studied
- Selecting suitable data is crucial in successfully detecting environmental change
- At a minimum you need to know the required:
o** Level of spatial detail**
o Region of the electromagnetic spectrum
o Frequency of re-visit
o Temporal dimension**
1. Level of spatial detail
- More detail generally implies less area covered by single image and bigger file size
Examples:
o Moderate resolution (>25m) is suitable to detect amount of forest lost or gained in an area
o Very fine resolution (<1m) is needed to detect changes at single tree leve
Level of Spatial Detail: Spatial resolution
Coarse scale
* Ice sheets
* MODIS
Moderate scale
* Land cover
* Landsat
** Fine scale**
* Individual trees
* <1m
2. Region of the Electromagnetic Spectrum
- Specific regions of the electromagnetic spectrum where the change occurs
- Satellite sensors have different spectral resolutions
Examples:
o Broad classes, such as dead or live vegetation, can usually be separated using few, wide bands(like visible, NIR)
o More specific classes, such as different rock types require comparison of many, narrow bands
**the more specific we are trying to get (in terms of category) the more spectrum information were are going to need the more bands we are gonna need **
Region of the EMS:Spectral Resolution
- Vegetation health
o Red
o NIR - NDVI
- Land cover (vegetation, rock,
soil, water)
o More bands needed
3. Frequency of re-visit
How often do you need to see an area to characterize the change?
Examples:
o Logging/cut blocks
▪ 16-day re-visit sufficient
▪ Landsat
o Fire progression
▪ Daily (or finer)
clouds can also get in the way of that
4.Temporal Dimension
How long do you need to collect data to be able to characterize the change?
Varies with the scope of study:
Examples:
o Changes in climate are slow, require long term information (>10 years)
o Area burned after a fire event is a fast change, require short term information (a week or two)
- Aerial imagery is available for the last ~100 years, while satellite only for the last ~50 years
Three Types of Change from Remote Sensing
Cyclical
Abrupt
Gradual
Data Requirements
- As we talk about different kinds of change, and specific examples
- Consider the data requirements necessary to detect those changes
- What level of spatial detail is required?
- i.e. spatial resolution
- What region of the EMS is required?
- i.e. spectral resolution
- What frequency of re-visit is required?
- i.e. temporal resolution
- What temporal dimension is required?
- i.e. how long do we need to be collecting data for
Cyclical
Season Cycles
A few examples:
- Temperature
- Day length
- Snow cover
- The greening and browning of
deciduous vegetation - Animal migration
- Animal hibernation
- Canadians going to Florida each
winter! - Our hobbies
o Ski in the winter
o Hike and bike in the summer
Cyclical Patterns
A pattern that repeats over time
- We will focus on:
o Phenology/vegetation cycles
▪ Camera traps
▪ MODIS
Seasonal Cycles of Snow and Vegetation
- As temperature warms in the summer:
o Snow melts
o Vegetation greens up - As temperatures cool in the fall:
o Snow returns
o Vegetation browns
