There is still a lot we do not know about the impacts of climate change on sea turtles and their habitats. By monitoring how conditions are changing over time and how these changes affect turtles, we can get a better understanding of how populations may be affected in the future. Baseline information and trends can be used to guide management decisions and evaluate their success. Monitoring can also encourage stewardship by involving the public in monitoring activities.
These are general reasons for monitoring but you should have specific questions that you want to answer. This will help you develop your monitoring plan.
It’s impossible to monitor everything so decide which questions are most important for where you work. What you monitor depends on the questions that you want to answer. Table 1 shows some of the main impacts of climate change on marine turtles and their habitats. Increasing beach temperatures, the impacts of sea-level rise on nesting area and how changes in precipitation are affecting nesting are three issues of concern for many marine turtle conservation groups. Maybe you are seeing some of these changes and want a better understanding of how they are affecting nesting turtles or egg development. It’s important to consider at the planning stages what questions you want to answer.
Several issues need to be considered at the outset to ensure that the monitoring program can be maintained long term and that the results are useful and meaningful. The main reason for failure of long-term monitoring projects is lack of consistency between surveys and in data recorded. These issues can be minimized with careful planning in the initial stages. The aims and objectives of the study need to be clearly stated, the methods carefully researched, reviewed and trialed and a means of easy data storage and dissemination of results established. For these reasons it is suggested that a coordinator is appointed to set-up and oversee the monitoring work.
The resources you have available in terms of time and money will also determine what you can monitor. Initial selection of indicators should be based on the specific questions to be answered, ease of measurement, time available, seasonality, labour and equipment availability. As the project evolves, additional indicators can be added. A standardized methodology should be used to reduce subjectivity and ensure that data are comparable among years.
Before you start, design your monitoring plan. Some questions to consider:
- What questions are we trying to answer?
- Which data will be used to answer those questions?
- Who will collect the data and when? Do they need training before they begin?
- Do we have all the equipment we need or the funds to buy it?
- When will the monitoring take place?
- Where will the data be stored so that they can be accessed by those that need them?
- Who will enter and analyze the data and report the results in the short and long term?
Asking these questions at the outset will improve your chances of having a successful long-term monitoring program.
Most projects have limited staff and time available for monitoring. The most important thing is that monitoring is done consistently so that the data collected can be compared over time. It is better to monitor a few things well and regularly than try and do too much and find you cannot maintain regular monitoring.
Beaches are naturally dynamic and can change considerably over time. Sand is added and taken away all the time and a beach may disappear and return over a few months, depending on the frequency of storms or high waves that remove large quantities of sand. Loss of beach area may happen when there is not enough sand available to replace sand lost to the sea. Changes in sand availability can happen due to the construction of structures that affect the movement of sediment, such as groynes, sea walls, ports, etc. or due to changes in sediment input into coastal systems, e.g. from changes in land use up river. As sea-levels rise, many beaches will naturally shift landwards and reconfigure so they do not lose any area. In other places where the natural movement is prevented by walls, buildings, etc. behind the beach, sea-level rise will lead to narrower beaches. Some beaches are more vulnerable than others to area loss. To determine whether beaches are losing area, it is necessary to monitor erosion and accretion patterns over time. From these it is possible to get an idea of the overall trend.
Measuring beach profiles (a measurement of the elevation or height of the beach surface taken along a line that runs from the dune or back of the beach to the water across the beach) in the same location over time can show changes in beach width, height and area. When multiple profiles are measured on a beach, you can get an idea of how the whole beach is changing and whether it is eroding (becoming narrower) or accreting (becoming wider).
Useful things to measure include:
- Change in beach width over time
- Change in beach/nesting area over time
- Trends at individual beaches
- Rate of change
This information can be used to determine how much nesting area might be available in the future as well as for management. For example, one response to eroding beaches that are not yet developed is to have setback regulations that determine how close buildings can be to the high water mark. Knowing how much the beach is moving over time helps to determine how far the buildings need to be set back.
This depends on how long the beach is, how variable the beach is in terms of its width and height and the time available for monitoring. If you have a long straight beach with roughly the same slope all the way along, you could set up equally spaced profiles along the beach. If the slope or width of the beach is very different in different sections then you want to sample in those different sections. It doesn’t matter if the profiles are evenly spaced, what is important is that they are always measured in exactly the same spot. Work out how long it takes you to measure one profile. You will probably get a bit quicker with practice but once you know that, work out much time you have available for monitoring and then how many profiles it is feasible to monitor.
Beaches often change seasonally so it is useful to measure them at least once every three months. You can always add in extra measurements if the beach suddenly changes, e.g. after a severe storm. You might also be interested in examining the recovery of the beach after a storm and do more regular monitoring, such as on a weekly basis, until the beach recovers. This can be added into the regular monitoring schedule.
Ideally you want to start the profile as far back on the beach as possible. The beach may shift a lot over time. Wherever you start from, make sure: i) there is a clearly marked, permanent marker (e.g. a tree, building, post), ii) that you start from the same spot every time and, iii) that the transect runs in exactly the same direction every time. You can use a compass to measure the direction of the profile.
There are different methods for measuring beach profiles. Check the Guidelines for Monitoring Beach Profiles for two simple methods and equipment lists.
Abney levels are available at survey or engineering supply stores. They cost anywhere between US$ 50 and 250. If possible, go for a larger one – the scale is much easier to read. If you are really on a tight budget, you could also make your own.
Some of the key gaps in our knowledge of how climate change will affect sea turtle populations relate to the effect temperature will have on aspects of reproduction and the reaction of sea turtles to those changes. By monitoring beach and nest temperatures over time it is possible to determine to what extent beach temperatures are changing and how they are affecting sea turtle sex ratios and survival. Through measurement of temperatures at different beaches around the world, we can gain a better understanding of how marine turtles might be affected in the future across their range.
One of the key questions when considering future temperature changes is what the effect on sex ratios will be. Current beach temperatures can be used to predict sex ratios, and may be used to reveal the extent to which beaches in the region are predominantly female- or male-producing. At a local level, adequate monitoring of beach temperatures enables visualization of differences in vulnerability to overheating within the nesting area, and management can be designed accordingly. Knowledge of temperature ranges within the nesting area can facilitate the design and implementation of adaptation measures, such as, for example, reforestation to provide shade to open beach areas.
Soil temperature and air temperature are interrelated and in general warmer average air temperatures are expected to lead to warmer soils, however, it’s a bit more complicated than that. Sand temperature is determined by a whole range of different factors that vary among beaches, so there is not a direct correlation between air temperature and sand temperature at nest depth. Soil temperature is regulated by a number of factors that include: (1) geographic variables, including latitude, slope, and aspect of the beach; (2) meteorological conditions, such as surface solar radiation (amount of heat from the sun that reaches the earth) and amount of rainfall, (3) site characteristics, including presence of vegetation, drainage, microclimate, and water table; and (4) physical properties of the soil, such as colour of the soil, water content, sand texture and organic matter content. The daily fluctuations in temperature seen at the surface are dampened by the sand and so there is not as much daily variation in sand temperature at nest depth. This is another reason why it’s useful to measure both air and sand temperature at individual beaches.
Two of the most popular are Hobo and TinyTalk data loggers.
- Not knowing why you're collecting the data
- Not storing information where it can be retrieved in the future
- Not giving precise information about where data was collected
- Collecting more samples than can possibly be analyzed
- Changing the methodology
- Not thinking about how you are going to analyze the data before collecting it
- Not analyzing data
- Using methods without questioning whether they are appropriate in your situation
Read up on different methods and decide on the best one for your project.
- Temperature Monitoring Manual
- Sea Turtle Nesting Beach Characterization Manual
- Guidelines for Monitoring Beach Profiles