EVSC 491
Problem Analysis: Ecology and Management of Pacific Water Shrews
Pacific Water Shrews
The pacific water shrew (sorex bendirii), hereon in referred to as PWS, is a fairly
large shrew, as shrews go in British Columbia. Adults are ~154mm in length and
~10.6 g in weight. They are dark colored with dark brown tails. They occur in
northern California through western Oregon and Washington, but in BC they are
restricted to the southwest.
In BC, PWSs inhabit dense wet forest of western red cedar where there are riparian
and stream habitats. PWSs are endangered in BC and they face threats to their
terrestrial and aquatic habitats from various human activities. Read the species
accounts provided in your courseware package.
Objectives
Assume that you are an environmental scientist working for the BC Ministry of
Environment. For your problem analysis, consider PWSs and their habitat in
relation to forest, agricultural, and recreational practices. Hypothesize about the
effects of various practices on PWSs and their habitats. Propose a conceptual model
(flow chart-type model) of habitat and abundance of PWSs. Incorporate the effects
of various practices as expressed at both the local and landscape level. Your model
should take a broad approach. For example, consider not only what happens at
specific sites during specific seasons, but also, consider what processes occur over
the long term and over the spatial scale of a landscape (i.e., several watersheds).
Identify factors that you think are important and hypothesize relationships between
these factors and PWSs, and where appropriate even between the factors. Address
the following questions: 'What effects will various practices have on PWSs
populations?', 'What effects will these practices have on PWS productivity?', and
'What guidelines and recommendations can you offer resource managers to assist in
managing PWS populations and their habitats in British Columbia?'.
How to Begin
Begin by considering the life requisites of PWSs. Think of factors that would affect
the abundance of PWSs. Identify factors that you think are important and
hypothesize relationships between these factors and PWSs. Identify specific
relationships and then combine them into a general model that retains its utility
over a broad range of habitat types and situations. The following questions will
provide a starting point and stimulate ideas.
1. Which factors are important to populations of PWSs: food abundance,
diversity of food, temporal (seasonal and inter-annual) availability of food;
security cover; thermal cover; quality and diversity of habitat types; mortality?
2. Which spatial variables are important: distribution of food sources; location
of resting sites; distance to streams and wetlands?
3. What things could be done to reduce, maintain or enhance the habitat quality
for PWSs? Explain your reasoning.
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4. Can the management and conservation of PWSs be compatible with human
use of land for settlements, resource use (e.g., logging, agriculture), and
recreation? Explain your reasoning.
To get you started, hypothesize (draw) the relationship that you expect between the
abundance of PWSs (y-axis) and size of a stream (x-axis). The x and y axes can be
scaled from 0 (low) to 1 (high). What assumptions did you make in drawing this
relationship? Draw the relationship between density of PWSs and density of coarse
woody debris on lands near streams (i.e., downed wood) (x-axis). Provide the
biological rationale for the shape and direction of this graph. Consider how your
relationships may change in the context of various land management practices.
Identify other relationships that you think are important.
Integrate these various graphs and hypothesize the relationships that you would
expect between PWSs and habitat characteristics. What land management practices
would you recommend to ensure that the habitat requirements of PWSs are met in
the area? Think of ways to enhance the value of various areas as PWS habitat.
Consider the implications of your relationships to your overall PWSs-habitat
management strategy. Think of ways in which human use of land can coexist with
PWSs. Think outside the box.
Content of Your Problem Analysis
Identify components (variables) that you think are important. Try to formulate the
relationships that you expect among these components. Draw your hypothesized
relationships between variables, for some you will just have to take your best guess.
Provide a short biologically or geographically based rationale for each relationship
that you propose. After you have identified these relationships, combine them into a
PWS-habitat model. This conceptual model is likely represented best as a "box and
arrow" model (a flow chart) that combines all the important factors in the PWShabitat system. As you build the model and integrate the factors, other variables or
relationships may emerge which you consider important. Integrate these new
variables into the model. As your model develops, some of the original variables
may appear trivial, so delete them from your analysis.
Which variables or factors do you think are the most important and likely driving
the system? If the Ministry of Environment provided you with some time and
modest resources (dollars, technicians, etc.), what information would you collect
and what research projects would you conduct to refine your model? Try to be
realistic in terms of your time frame. Remember that the surrounding area is a
desirable place to live; as time proceeds more habitats will be altered. You will
either contribute to the planning and management process or it will stagger on
without your input and direction.
Some Advice
You will not find the answer to this problem analysis in the literature, so do not
waste your time trying looking for it. The literature will give basic environmental
and biological facts, but you will have to rely on your imagination for the rest. Be
creative. Use ecological principles and common sense. Your model is an integration
of many hypotheses. It is your best guess of how wildlife-habitat systems are
structured. If you were to test your model and its specific hypotheses: what
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questions would you ask, what variables would you measure, and what experiments
would you conduct?
Your problem analysis is due 16:00 (4 pm) on August 31 but do not leave it until
August 30 to work on it. It takes time to generate ideas. Think about it, discuss it
with your colleagues, and then draw a few graphs (these are hypotheses, parts of
your model). Think a bit more, draw a couple of graphs, and so on. Be creative, do
not let technical limitations or lack of data constrain your imagination. Although I
encourage you to discuss the problem analysis with you colleagues, your submitted
report must be an individual effort. If you become stuck, need clarification or need
someone to bounce ideas off do not hesitate to talk to your instructor or colleagues.
I expect different students will have different models; there is not a single right
answer. You can emphasize areas of environmental science for which you have
trained. Hence, although all models should have all major components and factors,
some models may have an emphasis on more specific aspects of geography, water
quality, biology or whatever.
Begin your report with a short introduction and where you state your objectives (½¾ of a page). Use a "box and arrow" model to illustrate the structure of and
relationships in your PWS-habitat system. Confine your model to an 8 x 11 sheet of
paper. Use figures to describe relationships between variables. Place these figures
next to each arrow. Your model is essentially a whole bunch of small graphs
showing the relationships that you expect. For the most important relationships,
redraw them on additional 8x11 sheets and provide brief bulleted rationales.
In your discussion, identify the most critical factors and the most critical pathways
in the system and explain how they affect your objectives. Suggest processes or
relationships that could be studies to help advance management and conservation
of PWSs. Type your problem analysis but you can hand draw the figures if that is
easier. Use a black pen to draw figures and graphs. Please avoid using pencil or
colours to draw figures and graphs because they cannot be photocopied easily. Your
report should be about 15 pages long including the figures and systems model.
Copies of selected problem analyses will be sent to biologists in the Ministry of
Environment.
Logistics
10-14 pages +any literature cited, figures (graphs) and tables
Citation form: Student’s choice, note: must be consistent
Double Spaced
Times New Roman
Submitted: Electronically to instructor with subject line “PWS Problem Analysis”
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