Marco Nurmi, SYKE, 6 December 2019
Human impact modelling typically seeks to assess how strong the cumulative impact of anthropogenic ecolog-ical stressors is on the ecosystem, i.e. where nature is experiencing stress due to human activities. Impact mod-elling might in some cases assess the impact of only one specific stressor or activity; in other cases, the ecosystem and its components might not be included at all in the analysis, resulting in a product that estimates the amount of stressors present but not their impact.
The process of human impact modelling can roughly be divided into two stages: data processing and analysis. In the first stage, geographic information system (GIS) soft-ware like ArcGIS and spreadsheet programs like Microsoft Excel are usually the main tools used to process ecosys-tem and human activities data, with custom scripts used as support (though scripts can also be used as a main tool). In the second stage the processed data is entered into a program or script that calculates the cumulative impact.
Typically, the ecosystem is represented by a collection of ecosystem components, each as a separate spatial dataset. Examples of ecosystem components are seabed habitats or different mammal and fish species. Ecosystem components can also in turn be aggregates of several datasets or be composed of only a single dataset. If we take whale occurrence data as an example: the occur-rence of all whale species could be aggregated into one ecosystem component, or they could be divided into a couple of ecosystem components based on specific spe-cies traits or taxonomy, or each whale spespe-cies could be left as a separate component. What is the best approach depends on things such as data quality, scale, objectives, computer processing power, and time.
Human activities are often divided into stressors, or pressures, much in the same way as the ecosystem is
divided into ecosystem components. A single human ac-tivity, ship traffic for example, can cause several different types of stress on the surrounding ecosystem. Thus, the ship traffic dataset might be processed into two or more stressor layers, one maybe representing the underwater noise caused by ship machinery and propellers, the other representing the re-suspension of sediments caused by ship passage. Furthermore, these stressor layers might be aggregated with other stressors of the same type, com-bining all noise stressors into one dataset for example.
The first step when preparing and processing raw human activities data is usually the conversion data into the GIS format needed for further processing. The desired format in this stage might be raster, polygon, point or line, depending on the activity, scale, data quality, or stress it produces. The simplest way of assessing the extent and intensity of a pressure is to take the spatial data of the corresponding activity, and calculate how many times that activity is present in each location (raster cell).
Another simple method is creating a buffer around each feature (activity) to simulate the spatial extent of the pressure caused by the activity.
Simple methods for processing data are in some cases perfectly suitable, for example when calculating how much of the seabed surface is lost from dredged mate-rial being deposited there; other times, however, more advanced methods and tools are needed to estimate the extent and intensity. Advanced methods might take into consideration the diminishing effects of a stressor when the distance to the source of the stressor increases or when there are obstacles in the way, weakening the propagation of an expanding stressor like underwater noise. Advanced methods might also account for varying intensities within an activity, for example by considering ship size and speed when calculating physical distur-bance caused to the seabed. With ArcGIS, these
phenom-ena can be accounted for using tools such as ring buffer, focal statistics, Euclidean distance, cost path, viewshed, zonal statistics, and many others.
Ecosystem data processing can require similar methods as stressor data processing, but is often more straightfor-ward due to the stationary and present/absent nature of many ecosystem components, such as substrate type or seagrasses. Typically, the majority of ecosystem com-ponents are presented as presence/absence data (1/0), while stressor data tends to be a fairly balanced mix of presence/absence and continuous (0.01 – 1.00) data. For both ecosystem components and stressors the final pro-cessed data is almost always in raster/grid format. Expert opinions and scientific literature are the main sources when deciding how a dataset should be processed, for example when determining the size of buffers used to simulate the spatial extent of a pressure.
When all datasets are processed, the actual cumulative impact analysis can finally be run. All datasets are fed
analysis. Software suitable or meant for human impact modelling includes ArcGIS, Zonation, and ImpactMapper.
At this point, so called sensitivity scores or “weights” (Fig.
4.) are also entered into the software; these determine how strong the effect of a specific stressor is on any spe-cific ecosystem component when they intersect. Sensitivi-ty scores are Sensitivi-typically based on expert opinions.
The main final product is usually a quantitative map that shows cumulative impact, i.e. where and how much the ecosystem is under stress. Typically, the more ecosystem components and stressors there are present in the same area, the higher the cumulative impact value will be.
Human impact modelling is a concept that is still in a relatively early stage of development, especially when the focus is on the marine environment. New methods are constantly being developed, better data is becoming more available, and computer processing power is steadi-ly rising, leading to new opportunities almost every year!
1. (Photo by Essi Keskinen, Metsähallitus)
2. Diver taking samples. (Photo by Johanna Kantanen, Metsähallitus) 3. Safety training is an important part of our work.
(Photo by Eveliina Lampinen, Metsähallitus) 4. Team of two divers ready to start the dive.
(Photo by Anna Soirinsuo, Metsähallitus) 1.
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Diving
Suvi Saarnio, Metsähallitus, 20 December 2019
Diving is one of our three main methods for collecting biological data from the Bothnian Bay. The other two are drop-videos and wading.
When we want species data from deeper than 1 meter we do a 100 m transect line or dive points (which are basically the same as wading points, only done with the help of dive gear). Wading cannot be done in deeper than 1 meter because at that depth we cannot see the bottom substrate or the species that well anymore and there is a big chance for losing valuable information.
With drop-videos we can do mapping in deeper areas but we cannot get accurate species information with species coverage.
Diving is time consuming but it is also our most valuable method. Usually we choose the dive site carefully in ad-vance at the office and on the field we just drive the boat to the right spot and start putting the 100 m transect line down. Often the other end of the transect is put on a shore of an island and the other end goes straight out from the shore. We mark both ends of the transect with a buoy so that the divers can find it easily and so that it is easy to see that there is something going on in the water and that people driving boats should be aware. We of course also have a dive flag on the boat when divers are down.
We have to have a team of three when diving. We can choose if two divers go down and one dive supervisor stays on the boat or if one diver goes down with a rope and two supervisors stay on the boat and communicate with the diver by giving signals with the rope. The team of three is very important for safety because usually two persons are needed for pulling one person up to the boat from the sea and for transporting the victim to the shore.
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