Cave Ecosystems
December 2013
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Table of Contents
1. Introduction
2. Location: world
3. Location: Australia
Case study: Yarrangobilly
4. Air photo
5. Cave climate
6. Climate: entrance
7. Climate: twilight zone
8. Climate: dark cave
9. Landform: cave formation
10. Landform: cave decorations
11. Landform: karst
12. Ecology
13. Cave ecosystems
14. Food pyramids
15. Animal adaptations
16. Human impact: catchments
17. Human impact: caves
18. Management: karst
19. Management: cave
20. Management scenario
A Workbook has been developed for use with these study notes. Print the workbook at
the end of these notes and complete
Data Logger: temperature & humidity graphs have been included for the north Glory
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1. Introduction
"They are severely disadvantaged by quite minor disturbances. Thus they have low resilience in the
face of a change to the cave ecosystem......... conserving cave biota is a major challenge for ...
D. Gillieson. 1996
Cave ecosystems are very fragile because cave animals have evolved to survive in a very stable,
unchanging environment.
Caves themselves are also very fragile. The dissolving of limestone to form caves and its reverse,
the deposition of pure calcite to form cave decorations (speleothems) depends on a very fine
chemical equilibrium which either dissolves or deposits calcium carbonate.
o This equilibrium is influenced by the catchment above the cave including geology, soils,
climate, the water cycle and vegetation.
o Inside the cave it is influenced by carbon dioxide levels, humidity, groundwater flow and
Small changes by people to the catchments above caves or the caves themselves can have a major
impact on the caves and their ecosystems.
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2. World location
The world map shows the approximate location of limestone geology where limestone caves are
Longest Caves
Mammoth Cave sys.
Jewel Cave
Sieben Hengste ..
Windy Cave
Lechugilla Cave
Fisher Ridge Cave
Gua Air Jernih
Country Length km
Switzerland 156
Switzerland 126
Malaysia 102
Deepest Caves
Depth (m)
Reseau Jean-Bern...
Gouffre Mirolda......
Shakta Vjacheslava
Sistema Huautla
Sistema de la Trave
Illaminako Ateenoko...
Lukina Jama
Sistema Cheve
Tables from D. Gillieson, Caves, Processes, Development, Management 1996
Keep in mind that the above list will change as cave exploration continues.
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3. Location in Australia
Australia has over 10 000 caves. The map shows the location of some caves
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4. Yarrangobilly Caves: vertical air photo and topographic map
Vertical aerial photograph of the main tourist areas of the
Yarrangobilly Caves system. Source of air photo and topographic map:
© Land and Property Information Panorama Avenue Bathurst 2795
Gorge at top left of photo.
Map scale: one grid is one kilometre
North is to the top; contour interval is 10 metres
photo at right: cliff located at GR342459.
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5. Cave Climate
The temperature graph shows the difference between the outside temperature and that deep within the
caves. Being inside a cave is like being inside an insulated box such as an Esky. The surrounding rock
insulates the cave from temperature changes, both diurnal (daily) and seasonal. The temperature inside a
cave is very close to the average annual temperature outside the cave.
When compared to the outside climate, caves have:
high humidity
cooler temperatures in summer, warmer in winter
higher carbon dioxide levels
no light
no rain
no strong winds
very small seasonal and diurnal changes
Data Logger Results 23 October to 10 November 2010 for North
Glory cave (Yarrangobilly) Download the graphs of temperature and
humidity taken at the cave entrance and 10 metres past the entrance
gate, dark cave area. Temperature and humidity were automatically
recorded each hour.
Compare the variability and range of temperature and humidity for
the entrance and dark cave environments.
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6. Climate of the entrance ecosystem
You are walking down to the North Glory Cave to take readings
of the physical environment. It is a hot February day around
midday with a temperature of 330C, very low humidity of 29%
and no wind. As you approach the cave entrance you feel a cool
breeze coming from the cave. These are your readings at the cave
Hygrometers allow the relative humidity to be calculated. The dry
bulb thermometer is just a normal thermometer recording air
temperature. The wet bulb thermometer has a wet cloth around the
bulb. As this moisture evaporates, it cools the thermometer. To
calculate the relative humidity, get the difference in temperature
between the dry and wet bulb, in this case about 70C. Then go to
the dry bulb temperature at it's reading of 220C and go across to
column 7 at the top of the table. The relative humidity is 38%.
Light meters record light intensity in lux.
Anemometers record wind speed. In this case
the wind is blowing out of the cave entrance.
The speed is recorded in metres per second
How much cooler is the entrance of the cave to the outside temperature?
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7. Climate of the twilight ecosystem
You now walk into the cave about 50 metres to record
the environment of the twilight zone. There is still
some light to see by but not much as you notice there
are only a few low light tolerant plants present.
The diversity (number) of plant species is
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8. Climate of the dark
You now walk deep into the cave until
There is no light at all and repeat
your measurements
How much lower is the temperature here than outside the cave?
How would the change in light levels affect plants?
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9. Landforms: cave formation
Many landforms form from the breaking down of rock (weathering), the removal of the
weathered material (erosion) and the deposition of the eroded material. Landforms include
hills and valleys, floodplains, beaches, karst (limestone areas) and limestone caves.
Cave formation is much more complex than the above explanation. Individual caves form
over very long periods of time and cave forming factors such as climate, catchment water
flow, vegetation and soils change which impacts on cave development.
Once a cavern has formed and has air space, the deposition of calcite can occur and cave
decorations (speleothems) such as stalactites and stalagmites can begin to form.
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Fossil in the limestone at
Yarrangobilly which
formed about 440
million years ago from
the shells and skeletons
of sea animals and lime
Solution flutes caused
by rainwater flowing
down the rock and
dissolving the
limestone (chemical
Soil pH is a measure of whether soil is acid
or alkaline. This test is done by placing 2
drops of universal indicator on the soil
sample. The indicator turns a colour
depending on the pH. Sprinkle the soil with
barium sulphate (a white powder) which
shows the colour better.
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10. Cave decoration formation
Limestone is mainly made of calcite. When water containing dissolved calcium and
carbonate drops from the cave ceiling a small amount of the calcium and carbonate is left
behind (precipitated) as calcite, forming cave decorations (speleothems) such as stalactites.
Stalagmites grow from the floor up from the deposition of calcium carbonate from drops of
water landing on the cave floor (below left). Stalactites have formed along joint lines in the
limestone where water has seeped through (below right).
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11. Karst catchments
Karst is the term used for the distinctive landforms of catchments on limestone and other
soluble rocks. Karst landforms include:
underground drainage where water has dissolved the rock forming caves
gorges and sink holes which capture surface streams leaving dry valleys.
The topographic displays some of these features with a gorge in the area of the Natural
Bridge (a cave where all of the Yarrangobilly River runs through a hillside) and sink holes
capturing creeks.
Scale: each grid is one
contour interval 10 m
Source: © Land and
Property Information,
Panorama Avenue
Bathurst 2795
Above left: gorge and cave upstream of the Natural Bridge
Above right: Collapsed roof, Glory Hole Cave, Yarrangobilly
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12. Ecology
Caves can be divided into three zones depending on how much light they receive: entrance,
twilight and dark.
Light is a major factor limiting the size of the food chains and webs in an ecosystem. Food
chains show the flow of energy from sun to plants, which use light in photosynthesis to make
food, which is then passed on to herbivores and carnivores. As the amount of light decreases,
the amount of energy driving the food chain decreases, the number and size of plants
decreases and fewer numbers of animals can be supported.
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13. Ecosystems
Entrance Ecosystem. The entrance to the cave is
a transition zone between the outside and the dark
cave ecosystems. The climate of the entrance is
modified by the cool air of the cave. The hillside
below is opposite the cave and is covered with
typical eucalypt woodland. The cave entrance has
shrubs including banksias, grevilleas and tussock
grasses but no trees.
Twilight Ecosystem. As the amount of light decreases, in this case about 20 metres
into the cave, the diversity and number and size of plants also decreases. This cave has
ferns, lichens and algae growing on the rock.
Dark Cave Ecosystem. There is an absence of plants
(no sunlight for energy) and hence a lack of food
provided for the typical above ground food chain based
on plant photosynthesis.
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14. Ecology: Food pyramids and biomass
The cave ecosystem depends very much on food energy brought into the cave from the
surface environment. Food may be brought in by creatures such as bats, which leave their
droppings and their dead as food for other organisms. Air currents may bring in pollen and
small insects or floods in caves with streams may wash in debris such as wood and leaves to
be eaten by scavengers. The penetration of tree roots into cave passages may also be a very
important source of food.
With the absence of plants, most organisms are either detritivores or carnivores. This limited
productivity means that the total biomass of organisms is low and cave organisms are never
numerous. Dark caves have two distinct but linked communities. The roof community may
have bats ( not at Yarrangobilly) and the parasites which feed on them. This community relies
on journeys to the surface for feeding.
The cave floor community is more complex but relies upon the roof community for much of
its food. The organic layer on the floor is composed of the waste products and corpses of
animals from the roof as well as the floor. Woodlice, flies and beetles may feed on the guano
of bats. The carnivores then feed on
the guano eaters. These include spiders
and centipedes.
Plant Biomass (world
average from Krebs 1978)
Biomass is the weight of organisms
rainforest 45
present and gives an indication of the tropical
alpine 0.6 kg/m2
productivity of an ecosystem and the
dark cave 0.002 kg/m2
size of plant and animal communities woodland 6 kg/m2
supported. Biomass figures are a
convenient way of comparing different ecosystems. Compared to rainforests, caves have very
little food to support an ecosystem.
The biomass pyramids compare a
traditional pyramid to that found in
dark caves. These diagrams are
generalisations. Each cave has its
own pyramid; however, if drawn to
scale the cave biomass pyramid
would be over 20000 times smaller
than one for a rainforest. In deep
caves there is little to no light, so
the food chain has no direct source
of energy.
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15. Adaptations
Organisms have evolved very specialised adaptations, often quite bizarre to the very stable
cave environment.
General adaptations include:
a loss of pigmentation (colour)
partial or total loss of eyes
extension of sensory hairs or antennae
elongated legs
reduced size
changes to reproductive behaviour such as
fewer but larger eggs.
The cave cricket above has some but not all of these adaptations.
Cave animals are classified as:
troglobites which spend their whole life in caves
troglophiles live permanently in caves but can also live successfully in suitable
surface habitats
trogloxenes which return to the surface for food and include animals such as bats
Other Adjustments
With the absence of plants, most organisms are either detritivores (scavengers) or carnivores.
The lack of food energy means animals are never numerous and the total animal biomass of
caves is very small when compared to other ecosystems.
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16. Human impacts: karst catchments
Changes to catchments can have big impacts on the caves beneath.
Caves are part of the water cycle. Use of the land above caves changes the water cycle and
impacts on the caves. A eucalypt woodland was cleared in the Yarrangobilly Cave catchment
and planted with a pine plantation. The caves started drying out and it was discovered that the
pines used 17% more groundwater than the eucalypts.
The photo shows the pines are now being cleared and replanted with localeucalypt species to
save the caves.
The vertical air photo shows the area immediately around the Yarrangobilly tourist caves.
There are many wild caves in the catchment. The photo shows that area where caves are open
to the general public with the infrastructure necessary for this. Changes to the catchment
include vegetation clearing, gravel access
roads and various buildings.
Source: © Land and Property Information
Panorama Avenue Bathurst 2795
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17. Human impacts to caves
Small changes to caves can have big impacts on cave ecosystems.
Dark caves have no light and should not have green, photosynthetic algae. This lampenflora
has grown near lighting and will change the natural food chain.
Shoes leave mud which covers cave floor habitats and discolours cave decorations.
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Passages may be widened for easier access. This will change air flow, temperature, humidity
and carbon dioxide levels.
Cave entrances may be blocked by doors or grids to protect them from vandalism.
Unfortunately this may also change the air flow or access to animals which use the caves.
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18. Management: catchments
Why Protect Cave Ecosystems?
Biodiversity Value: Caves contain species of animals
which are rare and occur nowhere else.
Intrinsic Value: People value the spectacular
formations found in caves.
Utility Value: Tourism is an important industry.
Heritage Value: Limestone caves are a part of our
natural heritage. We only have a small number of
Limestone caves are uncommon in Australia and government
has protected many through legislation such as the NPWS Act.
The Yarrangobilly Caves are in Kosciuszko National Park.
Government legislation states that the National Parks and
Wildlife Service (NPWS) is responsible for protecting the
caves but at the same time allow use that does not conflict
with the preservation of the caves. To achieve this goal the
NPWS are required to have a management plan which outlines
their management strategies. Two main areas need to be considered, management of the
individual caves and management of the whole catchment above the caves.
Catchment Management
Catchments and caves are linked by the flow of water, surface water will flow or percolate
underground and any pollutants or eroded soil transported by surface streams may be carried into
caves. Human changes to the catchment will impact the water cycle and the caves. This includes
the clearing of vegetation, diversion of streams, the building of roads which change the flow of
water with roadside drainage channels, pollutants from
vehicles using roads or fertilizers and herbicides from
agricultural activities which can endanger cave
Catchment Management Practices in the
Yarrangobilly area include:
not allowing camping near the caves
retaining the existing buildings and infrastructure
of car parks, picnic areas and toilets due to their
historic and recreational value
working towards minimising the impact of infrastructure, roads and buildings on the
replacement of the pine plantation with the original eucalypt woodland
19. Management: caves
The NPWS has a dilemma in that it must protect the caves but at the same time allowing public access
to this extremely fragile ecosystem. The NSW National Parks and Wildlife Service manages caves at
Yarrangobilly according to the following categories.
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1. Public Access: Open to the public with a ranger or
2.1 Special Purpose: Two caves have been set aside at
Yarrangobilly as scientific reference caves to protect
their faunal communities. Access to these will be by
scientific researches holding NPWS Scientific
2.2. Outstanding Natural Value: caves with special
formations or ecosystems.
2.3 Dangerous: caves may be subject to flooding or
have dangerous drops.
3.1 Wild Caves: there are about 120 wild caves at
Yarrangobilly which require permits from the NPWS
to enter.
3.2 Unclassified Caves: closed until classified.
Specific cave management practices at Yarrangobilly
limiting tourist access to only a few caves restricting
public use to guided tours except for one self-guided
educating the public on cave fragility
only accredited caving groups, normally members of
the Australian Speleological Federation, will be
permitted to go caving other than at public access
all groups holding permits must abide by the Codes of
Ethics, Safety and Minimal Impact of the Australian
Speleological Federation
the use of caves for toileting, smoking or carbide
lamps is forbidden
cavers should follow a single pathway through caves to
minimise human impact
muddy shoes and clothing must be removed in delicate
areas to leave the passage mud free
camping or lighting fires near cave entrances is not
the maximum number of cavers on any one trip is 12 and the minimum 3.
each trip is to be undertaken by a fully experienced leader who is responsible for safety and
conduct of the group
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20. Management scenario
Cave features:
1. large cave with vertical shafts which require abseiling
2. small cave with bat colony and cave floor beetles living on bat guano
3. large cave which floods rapidly after storms
4. small cave with good variety of speleothems
5. good range of speleothems but they are not scientifically valuable
6. large cave with easy access, variety of speleothems but do not warrant special
7. cave has large chambers with variety of speleothems but human access is difficult
because of very small entrance and narrow passages between large caverns
8. large cave with small creek, easy access, variety of speleothems
Development Proposal
The present Caves site has been suffering from over use. Visitor numbers have exceeded the
carrying capacity of the public access caves and the cave decorations are getting damaged. Cave
temperatures have been rising 1.50C during tours from human body heat. You are a member of
the NPWS Speleological Planning Team and have been asked to investigate the opening up of a
new site shown on the map above which is about 10km from the present site. (For the purposes of
this exercise the original map has been modified to include an area of non-limestone rock.)
The Planning Team will submit a report to the Director-General, NPWS for her consideration. In
you report you will include the map above to show any proposed infrastructure developments and
a written explanation. Keep in mind that although there are only 8 cave entrances shown, the
caves themselves, extend under the whole limestone area. You will need to:
give each cave a classification using the NPWS scheme below
decide which caves you will allow public access to
the location of infrastructure including walking tracks, roads for vehicle access, toilets,
ranger office and information buildings and car parks for cars and buses (consider the
impact of soil erosion, possible water pollution and construction on the caves beneath)
you have been asked to pick the best position for an overnight tent camping area. It is
very unlikely this would be allowed but is to be included for discussion purposes
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where will power for such things as lighting come from?
people will walk to the river, it is a focal point. They will take their lunch and spend some
time there. You need to include a walking track to the river so you can plan the safest
route and the one which will cause the least damage to caves from soil erosion.
Prepare a management plan for each cave you decide is suitable for public access. How will you
allow public access but at the same time protect them for sustainable use? You will need to
location of access tracks to the entrance
internal cement paths and steps will destroy cave floor ecosystems and their construction
will cause much damage. Is there an alternative?
Protection from visitors who should not be there, perhaps either they have not paid for
admittance or do not have a guide
Lighting systems for safety and the display of special features require wiring and the
installation of other equipment. Is there an alternative?
Are any caves suitable to be self-guided or will they need a guide?
How many people will you allow in a group inspecting a cave?
Will you allow accredited caving groups, members of the Australian Speleological
Federation, to use some caves which are normally closed to the public? If you allow this,
how will you manage it?
Cave Classification Scheme.
Category 1 Public Access caves are open to the public and have been developed as public inspection
caves either with a ranger or as self-guided.
Category 2.1 Special Purpose caves are managed to keep them as unmodified as possible consistent
with some recreational use. Two caves have been set aside at Yarrangobilly as scientific reference
caves to protect their faunal communities. Access to these will be by bona fide scientific researches
holding NPWS Scientific Consents. Other caves will only be entered in the company of NPWS staff.
Levels of visits are be closely monitored.
Category 2.2 Outstanding Natural Value caves are also subject to limitations on numbers and
frequency of visits but not as strict as 2.1 caves. Parts of category 2.2 caves may be classified as 2.1.
Category 2.3 Dangerous No caves at Yarrangobilly have been classified as 2.3. Several entrances to
the Glory Holes caves have been classified as 2.3 to avoid dangers to tourists from cavers above.
Category 3.1 Wild Caves There are about 120 wild caves at Yarrangobilly which require permits
from NPWS to enter.
Category 3.2 Unclassified Caves are closed to access until classified.
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Data Logger Information
Temperature and Humidity Data Logger Information from north Glory Cave
Data loggers were setup in the cave to record temperature and humidity readings for the Cave
Entrance Zone and the Dark Zone.
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Cave Worksheet: (Not for the fieldwork trip)
For use in class with the web based Study Notes. Make copies of this worksheet and
complete in class using information in the study notes
1. Introduction
1. Explain why caves and their ecosystems are fragile.
2. World Location
a. Vegetation forms general latitudinal bands around the world with
tropical rainforests near the equator and tundra near the poles.
However the location of limestone geology where limestone caves
form does not follow a similar neat zonation. Describe limestone
geology under the following headings:
2i. latitude
2ii. continuity
2iii. size and shape
2iv. describe the world location of limestone caves.
3. Location - Australia
3i. Where are most Australian tourist caves located?
3ii. Describe the continuity of cave in Australia.
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4. Location - Yarrangobilly
4. What features are located at the following grid references (GR):
i. GR345453
ii. GR343454
iii. GR351459
4ii. What are the approximate straight line distances of:
Radio Hut to Jersey Cave
Thermal Pool to Jersey Cave
Jersey Cave to Ranger
4iii. What is the altitude of the following features:
i. Radio Hut
ii. shed at GR 349449
4iv. North is to the top of the map. What is the direction of:
i. Ranger Station from Thermal Pool
ii. Thermal Pool from Glory Hole Cave
4v. Landform
Describe the general landform using all of the information on the page.
5. Climate
5i. How does the climate inside caves differ to that outside? List 5 of the major differences.
5ii. Compare the seasonal temperature range inside caves to that outside in the Yarrangobilly
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5iii. In which months of the year is the temperature inside the caves warmer than the average
daily temperature outside.
6,7 & 8. Climate of the entrance, twilight and dark ecosystems
6i. Fill in the table using the readings on the instruments in the study notes.
climatic element
air temperature
(deg. C)
relative humidity
light intensity
wind speed (m/s)
6ii. Describe how the following change as you go deeper into the cave:
a. air temperature
b. relative humidity
c. light intensity
9. Landform: cave formation
9i. What is the term which describes the breaking down of rock?
9ii. Which type of weathering, physical or chemical, is mainly
responsible for cave formation?
9iii. How did the limestone for these caves form and how long ago did this occur?
9iv. Soil forms from weathered rock. Soil acidity (pH) is an important soil characteristic.
What is the pH of the soil sample tested? _________________________________________
10. Landform: cave decoration formation
4bi. Write the names of cave decorations (speleothems) on the diagram.
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4bii. Explain how stalactites form.
11. Landforms: karst catchments
11i. Name some of the major landform features found in karst catchments?
11ii. Calculate the average gradient from spot height 1143 m
to the river at the Natural Bridge.
(gradient = difference in height divided by horizontal distance
and is expressed as a fraction)
11iii. Why might using this gradient give the wrong
impression if you used it to describe landform here?
11iv. Construct a transect from spot height 1143 m to the
river at the Natural Bridge.
11v. Explain why are limestone areas are often dry on the surface?
12. Ecology
12i. What do food chains show?
12ii. Name the three zones in caves determined by the amount of light they receive?
13. Ecology: food chains
13i. Describe how species diversity (the number of different types of plants and animals)
varies as you move deeper into a cave from the entrance?
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15. Adaptations
15i. Draw a cave animal and list it's adaptations.
15ii. Explain why most cave animals are unable to survive minor changes to the cave
16. Human impact on catchments
16i.Explain why human activities in cave catchments have a large impact on the caves?
16ii. List some of the activities people do which change cave catchments.
16iii. Draw a precis map in the space showing
human changes shown in the Yarrangobilly air
photo.The topographic map on page 2c will help.
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17. Human impact in caves
17i. List changes made to show caves to allow guided tours.
17ii. Describe some of the impacts people have on caves when they visit them.
18. Catchment Management
18i. List four values we place on caves:
18ii. Explain how the government has protected caves.
18iii. Why is catchment management important?
18iv. Give three examples of catchment management in the Yarrangobilly area to protect the
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19. Cave Management
19i. Name the 6 categories of caves in the NPWS cave classification system often used to
assist cave management?
19ii. List 6 of the specific cave management methods used at Yarrangobilly.
19iii. Explain the dilemma for the NPWS when managing caves?
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Cave Ecosystems - Riverina Environmental Education Centre