RESEARCH AND MONITORING INSTRUMENTS
Remember that many details that may be important to scientists that must communicate their work to others will not be necessary if the information is just for your own use at the local level. For instance, scientists usually measure things using international systems of measurement such as metres, litres and grams, that make it possible for everyone to compare what they are measuring. If you do not have a metre stick, ruler or measuring tape, you can invent your own measures. For instance, a length of rope can be used for surveying (for example: 5 ropes from house to tree; 12 ropes from tree to fence, etc.). As long as the same length of rope serves as the unit, your measurements will be consistent, and if you keep the rope safely, it will always be possible to measure it later and make the conversion to standard units (if the rope is 5 metres, the distance from house to tree in the example would be 25 metres). A wooden pole can also be used as a unit of measure; it can be laid end to end, or used to make regular marks on a measuring rope. Long ago people used fingers, hands, arms and feet as units of measure. One English measure is still called the foot. Today it is often possible to find something already measured or marked off at regular intervals, like ruled paper, that can be used to make measuring devices.
Similarly, a simple balance can be built to give comparative weights or changes in weight. Two pans are hung from a rod that is suspended in the middle, perhaps with a wire or nail sticking up to show when it is level. Once it is adjusted so that it is level when empty, it can be used to weigh things by placing the object on one pan and counterweights on the opposite pan until it is again level. Today it is not hard to find things of uniform weight that can be used as counterweights and units of measure, such as coins, marbles, canned goods, fishing weights, etc. Some things even have their weights written on them.
Another approach is to record the measurements directly without using a system of measurement. For instance, if you are measuring the amount of rain every day in a rain gauge and keeping the record on a wooden board, you could put a dry stick in the rain gauge, then lay it on the board and cut marks with a knife showing the length of the stick that was wet. Such marks made along a line each day, with symbols showing the season or time of year, will produce a good graph of the rainfall. It is not even necessary to be able to read and write. The same technique can be used to measure the diameter of tree trunks or the length of fish; a string is wrapped around the trunk or laid along the fish, and then placed on a board or sheet of paper where the length is marked and identified.
Since most measurements for local environmental management will be for inventories or comparisons of changes over time, what is most important is that the same techniques and measures be used each time. Standard measures make this easier, but they are by no means absolutely necessary unless your information must be compared with that from other places. You will probably not need as much precision as a scientist in making your measurements, so the above techniques should give adequate results.
Fresh water is one of the most important island resources. It is therefore essential for agriculture, for village water supplies, for flood protection and other uses to know how much rain falls, when it falls during the year, how much can fall in a short period of time, how long are the periods without any rainfall, and how much these amounts change from year to year.
Most island countries have at least one weather station where rainfall is measured, and this information is usually available for the location of the station. However, rainfall can vary a great deal from place to place on an island, depending on whether it is the wet or dry side, high or low, exposed or protected, etc. It is important to understand how these places with microclimates differ from the main weather station. One way to do this is to make your own records of local rainfall, which can be done very simply by catching the rain in a rain gauge and measuring it.
It is sometimes possible to buy clear plastic rain gauges already marked with a scale showing the amount of rain. If these are not available, you can make one out of any can or cylindrical glass jar with straight sides, a flat bottom, and a mouth as wide as the sides. The container must be straight from mouth to bottom so that the depth of the water (the amount of rain) can be measured with a plastic ruler or other measuring stick. A clear plastic or glass container is better because you can read the depth through the side of the bottle.
The rain gauge needs to be placed in the open far from walls, roofs, trees or other things that might either shelter it from the rain or drain extra rainwater into it. It should be fixed upright where it cannot be knocked over, and where children cannot play with it or animals drink from it.
The rainfall is determined by measuring the depth of water in the rain gauge. This can be done with a ruler (like a child's school ruler) or other scale attached to the outside of a clear container, or by putting a ruler in the water and reading the level on the scale (be sure that the ruler reads from the very end; many rulers have a space before the scale starts, and this space will have to be cut off to measure the depth inside the container.
If no ruler is available, the depth can be measured by the direct method. Pick a stick or rod of a material that changes colour or otherwise shows clearly when it is wet. It should not be too absorbent, or the water will creep up it before you have a chance to record the mark. Dip the stick to the bottom of the container, then quickly place it on your record sheet and mark off the level of the water on the sheet. The stick should be as small and thin as possible, so that it will not raise the level of the water too much when it is put in the rain gauge. Be sure to empty the water out of the container after making the measurement, so that the gauge is ready to catch the next day's rain.
The ideal is to measure the rainfall every day at the same time of day. If this is not possible, try recording the rainfall every two or three days, or at least once a week, perhaps in conjunction with some regular activity like going to church. If you wait too long between measurements, the rain gauge might overflow if there is heavy rain, or if it is hot and dry, the rain water might evaporate before you measure it. If you miss a measurement, note this with your next measurement and either show the amount for the day when the most rain fell, or divide it evenly between the days which the measurement covers. If dirt or leaves get into the gauge, remove large pieces if possible before making the measurement, and clean out the gauge thoroughly before putting it back in place.
With each measurement, be sure to record the date and the number of days that the measurement represents. If there was no rain, this also should be recorded. One of the best ways to show rainfall patterns is to make a long bar graph with marks on the bottom line for each day or week of the year, and with bars showing the depth of the rain in the gauge for each day it fell.
As rainfall information is collected from year to year, it will become more and more useful. You can compare your rainfall with that at your nearest weather station. You can also compare the current year with previous years to see how much they change. You may also be able to relate rainfall patterns to the best time for planting or harvesting, to the fruiting of trees, the occurrence of plant diseases, or the numbers and behaviour of coastal fish. Such information can help to achieve the best management of your natural resources.
In the tropical islands, the temperature is not as much of a problem for resource management as it is in deserts or colder temperate areas. It is usually the extreme temperatures, such as particularly hot days or cold nights, that may have an effect on agriculture or housing design. However, the water temperature in the lagoon and coastal waters may be more significant for fisheries and coral reef management. Even a small change from the usual temperature may result in the death of corals or the disappearance of fish.
The temperature must be measured with a thermometer. There are no non-technical methods that are sufficiently accurate for monitoring temperature changes. Fortunately it is usually possible to find inexpensive household thermometers that are sufficient for local monitoring purposes. For measuring water temperatures in the sea, a thermometer with a plastic support is usually best, as paper will dissolve in the water and metal will rust or corrode.
To get the high and low temperatures during the day, it is best to read the thermometer in the middle of the afternoon when the sun is still high, and late at night or in the very early morning when it is coldest. A thermometer should always be hung outside but in the shade and not held where the hand could warm it while reading the temperature.
When taking the water temperature, the bottom of the thermometer should be in the water for at least 1 to 2 minutes before reading the temperature, and the reading should be made while the bulb is still in the water. There can be big local differences in the temperature of coastal waters depending on their depth and the amount of circulation, so be sure to choose a place where the water is representative of the environment you want to monitor. Ocean temperatures do not change from day to night, but only with the time of year. However, there can be some daily change in the temperature of shallow coastal waters.
The ideal thermometer for environmental monitoring is called a maximum-minimum thermometer. It is shaped like a U and has little metal slides inside that show the highest and lowest temperatures reached since the last resetting. The slides are usually reset with a magnet. With such a thermometer, environmental readings need only be taken at whatever time is convenient during the day, or even say once a week to record seasonal changes in high and low temperatures. Such thermometers are easy to use and not very expensive, but they may be difficult to find in most small island countries.
Turbidity is a measure of how cloudy or muddy the water is, based on showing how far light can travel through the water (sometimes called its transparency). Turbidity is a good measure of water pollution, or the effects of sediments or erosion on lakes, rivers, or coastal waters. Turbidity can be caused by fine silt, mud or soil in the water, by organic or chemical pollutants, or by dense blooms of tiny algae (plants) or animals which may grow quickly when there are fertilizers or other pollutants present. Monitoring turbidity is a good way of measuring the quality of the water or the health of a lagoon.
The classic way for scientists to measure the turbidity where the water is deep enough is with a Secchi disk, and it is so simple that anyone can do it. A Secchi disk is a circular disk usually 25 centimetres in diameter, attached in its middle along with a weight at the end of a rope. The disk is painted white, or preferably divided in quarters with two white quarters and two black quarters. The rope is measured and marked at regular intervals, usually every metre, so that it is easy to tell how long it is.
To measure turbidity with a Secchi disk, you need to be over reasonably deep water in a boat or at the end of a dock. It is best to measure the turbidity in the middle of the day when the light is bright. Avoid working in the shadow of the boat or dock. Lower the disk into the water and watch it go down, counting the length of the rope as it goes. When you can no longer see the disk, write down the length of the rope from the water's surface to the disk. Lower the disk a little more, then pull it up until you can just see it again, and count the length of rope from the surface to the disk as you pull it back up. Add the two lengths together and divide by two to get the average distance to where the disk was no longer visible. This distance is a measure of the transparency or turbidity in the water.
Depending on the circumstances, it would be useful to measure coastal turbidity once a week to get seasonal changes. More measurements would be needed after storms or pollution incidents. If the turbidity changes with the tides, currents or wind directions, then frequent measurements should be made under different conditions, or all measurements should be made when these conditions are the same.
CORAL REEF AND FISH MONITORING
The South Pacific Commission has already developed simple techniques for coral reef monitoring, which are explained in more detail in the Coral Reef Monitoring Handbook by Arthur Lyon Dahl (South Pacific Commission, Noumea, New Caledonia, 1981, and UNEP, 1984).
Fish populations along a coral reef can be estimated by swimming with a mask or goggles back and forth for 100 metres along the edge of the reef (measure the distance by following along a 100 metre length of rope). Fish are counted that are within about 2 metres of the rope on either side. On the swim out, count the number of large predatory (fish-eating) fish such as snappers, groupers and emperors. These fish are often the first to be caught by fishermen on the reef and their number is a measure of the fishing pressure; if there are none along the front of the reef, or their number declines over several counts, then there may be a problem of overfishing. On the swim back along the rope count the number of butterfly fish. These brightly coloured reef fish often swim in pairs and have a special way of biting and sucking around corals. If there are less than ten along the 100 metres of reef, or their numbers decrease with succeeding counts, then something may have damaged the reef ecosystem.
The coral reef itself can be monitored by surveying fixed points on the reef chosen as representative of what the reef is like. A piece of iron reinforcing rod can be driven into the reef to mark the survey spot permanently. A rope 4 metres long with a loop at one end to go over the rod is used to measure the circle to be surveyed, which is easily covered by swimming or walking around near the end of the rope. The bottom is first described as being mostly mud, sand, rubble, blocks or solid rock. Then an estimate is made of the amount of bottom covered by live hard corals, soft corals and sponges, dead standing coral, crustose coralline algae, and marine plants. The major shapes of corals, soft corals, and plants in the circle are noted. Finally large or conspicuous animals in the circle are counted.
The Handbook explains all these measures, and includes simple forms on which the information can be noted. When the survey is repeated in the same place, changes in the coral reef and its populations can be observed. An explanation of the possible meaning of these changes in included.
Simple monitoring techniques like these make it possible to follow coral reef resources closely and to observe what changes are taking place. With this information, and perhaps some expert advice if necessary, it may be easier to manage coral reef resources.
Forest areas can be monitored using methods similar to those described for coral reefs. In most small island forests, the bird populations are similar to the fish in the sea, and the trees and plants are like the corals and seaweeds. However, the size of the trees and the impossibility of swimming over them means that the method must be modified accordingly.
Forest birds can be monitored by someone who knows the local birds well by walking a certain distance (perhaps 1 kilometre) along a forest trail in the early morning and counting the number of each important kind of bird seen or heard. Some care is required to avoid counting the same bird more than once. Using this standard measure, changes in the bird populations can be measured from season to season and from year to year.
The composition of trees in the forest can also be monitored over time, using a series of survey circles. Select and mark one tree as the centre point in the survey circle. Do not always choose the same kind of tree as a centre point, but be sure you can find the tree again when you want to repeat the survey 1 to 5 years later. Take a rope marked at 1 metre intervals and tie it around the centre tree so that at least 10 metres of rope extend from the tree. The size of the circle can be made smaller or larger depending on the density of trees and the number of different kinds of trees in the forest. A larger circle is necessary if there are many kinds of trees, but if a circle has too many trees it will take too long to survey.
To survey the circle, use the rope to measure the distance to each tree in the circle, and write down on a piece of paper the kind of tree, its position and its distance from the centre tree. Measure only trees with a trunk large enough at breast height that two hands cannot reach around it. When the survey is repeated from the same tree, it should be possible by comparing notes to see which trees have fallen or been cut down, and which new ones have grown up to be large enough to count. The total number of trees and any changes in the kinds of trees in the forest can also be estimated.
Within the same circle, a count can also be made of any rare or significant animals or plants like orchids, or introduced pests like guava, lantana or the giant African snail. Changes in these counts over time can also be a sign that important changes are taking place in the forest.
The soil is one of the most essential island resources, on which both agriculture and forestry depend for their productivity. Careful management of the soil is essential to maintain its good qualities. To do this, it is helpful to be able to measure some of the characteristics of the soil and to monitor any changes. The following are some simple ways to analyze a soil for its qualities.
Soils are made mostly of sand, silt and clay. Sand has large grains that are easy to see with the naked eye. Silt has finer grains like the mud left behind where water has receded. Clay is the finest of all and usually sticks together in a slippery mass when it is wet, or becomes very hard when it is dry. The amount of each of these determines the composition of a soil and gives it its texture. A good soil, called loam, has about 15% sand, 30% silt and 55% clay.
An easy way to see the composition of a soil is to take a clear glass jar or bottle with a tight fitting top and straight sides that are easy to see through. Fill the jar less than half full with the soil to be tested, add water until it is almost full, put on the top, and shake well until the soil is thoroughly mixed with the water. Then set the jar quickly in a quiet place and do not move it for at least a day.
Look closely at the layers of soil particles in the jar. The largest and heaviest particles settle out first. Stones will be on the bottom, then sand, followed by silt and finally clay. Some fine clay particles may stay suspended in the water, and large particles of humus or organic matter like wood will float to the top. The thickness of each layer shows the proportions of that particle type in the soil sample.
The soil texture is the way the soil looks and feels, and it depends on how much of each kind of soil particle is in it. The texture or feel of a soil changes as these proportions change.
To test a soil for its texture, take a small amount of the soil and crumble it in the palm of your hand. Add a little bit of water to the soil and try to work it into a small ball. Use the questions and answers below to find the texture of the soil.
Is the soil gritty? NO YES Is the soil sticky? Does it make a firm ball? YES NO YES NO Is it hard to squeeze? Is it silky? YES NO YES NO Clay Clay loam Silty loam Loam Sandy loam SandBy following each soil sample through the above questions, you can determine the general type and texture of a soil.
Soil and water
One of the important characteristics of a soil is what it does when it rains and the soil gets wet. It is important to know how quickly water is absorbed or soaks down into the soil (called its porosity), how quickly it passes through the soil (its permeability), and how much water is held in the soil (its field capacity). If water is absorbed quickly into a soil, there will be less danger of its running off and causing erosion or floods. If it passes through the soil quickly, then the ground water will be recharged rapidly. If the soil holds a lot of water, then it will not dry out so quickly after a rain and crops will grow better. The following simple test will show how a soil rates for these qualities.
Take three cans of the same size, like those that beer or soft drinks come in, and remove the tops. Mark each can in the same place half way up, so that you can tell when the can is half full. Punch several small holes in the bottom of one can with a nail or other pointed instrument, and fill it half full with the soil to be tested. The soil should be dry and well packed down in the can. Fill another can half full of water. You will need a clock or watch that can time in seconds. Hold the can of soil over the empty can, pour the half can of water on top of the soil, and start timing immediately. Count the number of seconds it takes for the first drop of water to fall into the bottom can; this shows the rate that water passes through the soil (its permeability). Also count how long it takes for all the water to disappear from the surface of the soil, which show how fast the soil absorbs water (its porosity). Then wait for 10 minutes, and measure how much water is in the bottom can (remember that you started with half a can of water). This shows how much water stayed in the soil (its field capacity). You can measure the amount of water in the same way you measured the water in the rain gauge. Write down each of these figures for the soil sample.
There are no easy ways to test a soil for the amounts of essential nutrients for plant growth, such as nitrogen (N), phosphorus (P) and potassium (K), but it may be possible to buy a simple soil analysis kit from an agricultural supplier. If so, it would be good to test for these nutrients too, following the instructions supplied with the kit.
If you are testing the soil in a field or garden, it would be best to test at least three samples from different parts of the field with each of the above tests to see how much difference there is between samples. If you do the tests every year with soil samples from the same place, you can monitor the soil and see how it may be changing over time and whether management actions are needed to protect soil quality.
CENSUSING AND SAMPLING
It is often necessary as part of an inventory or monitoring programme to find how many there are of something, whether it be cattle on the range or people in the community. This can be done by making a census, which is a complete count of whatever is of interest. Governments usually make a census of the population every 5 to 10 years, counting the people in every family and village. A census requires either visiting every place where the count is to be made, or else gathering everything together for the count, as is often done with cattle.
When a census is repeated, it is possible to see what changes in numbers have occurred since the last census. Some may no longer be there, having died or moved away, and new ones may be added through births or immigration. The total change in numbers gives some idea of the rate of growth or decline, depending on whether there is an increase or decrease in numbers. Such figures are often important for environmental management. A census often collects data on age as well, since it may be important to know the age structure of the population, that is how many there are in each age group (often taken in 5 year groupings). This information shows if a population is getting younger or older. For people, knowing this helps in planning social services like schools, jobs or extra health care for the elderly.
Often it is not possible or not worthwhile to count everything as is done in a census, so it is necessary to take a sample, which is a part of the whole that may show something about the whole. Sampling is a very useful technique in research, but there is always a problem in knowing how much is a good sample. Whether a sample is good can be complicated, and depends on the total numbers involved, the distribution of the things being sampled (such as whether they are scattered at random, evenly spaced, or perhaps clumped together) and their diversity, or how many different kinds of things are mixed together.
To show the problem of sampling error, suppose something occurs in clumps of several individuals separated by large empty spaces. If your sample falls in the middle of a clump, you would have the impression that there are many of the things, but if it falls between clumps, you would think that there are few or none at all. With sampling there is always a problem of establishing what is a significant difference between samples, as opposed to a chance difference caused by sampling errors. Increasing the number of samples or the size of the samples reduces the error, but it also requires more work.
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Scientists often measure the chance of error in their samples in terms of the probability that the sample is good or that the difference is significant. Normally they will only accept a result if the chance that the difference in the samples is not real is only 5 percent or 1 percent. There are many statistical and mathematical tests to check this significance.
Another problem with sampling is that the person doing the sampling may be biased or may be expecting a certain result. Often the person is unaware of this effect, and he or she may not realize that an unconscious preference is affecting the choice of samples. Sometimes scientists use techniques to select the samples at random to avoid this problem. More samples may be needed with random sampling, but the result is closer to the true situation.
It is not possible in a brief review of research techniques to discuss this subject in much detail. What is important to remember is that you should not make judgements or base important decisions on too small a sample of environmental information or research. It never hurts to repeat something in order to confirm an earlier result. If the second result is different, then actions based on the first result might have been wrong. You may need to repeat an experiment or measurement several times to see how much of the difference occurs by chance (or sampling error) and how much represents a significant difference.