Whether orchids or mammals, insects or slugs and snails: nowadays there are a large number of animals and plants under observation. Researchers and dedicated activists work meticulously to record their distribution, count their numbers, and document every increase or decrease. Unfortunately, the collection of this data began only very recently. For this reason, it is very difficult for ecologists to assess how much biological diversity has actually been lost due to modern civilisation. The fact that the human impact on biodiversity is likely to be greatly underestimated is the warning sent out by an international research team headed by the UFZ in a recent study published in Scientific Reports.
Some of them count the birds at a winter feeder, others walk along a stipulated route, summer after summer, to identify the butterflies they discover along the way. For a long time now, numerous nature enthusiasts have been contributing to the inventory count of biological diversity. Similarly, universities, research institutes and authorities participate in extensive monitoring programmes to assess the state of fauna and flora. There is a clear aim to all of this effort: the objective is to document any changes and, to the extent possible, stop the loss of biodiversity. Where can which species be found? Are the populations increasing or decreasing? Which animals and plants are experiencing serious difficulties? And are the measures taken to protect them actually achieving the desired result? "Questions of this nature can only be answered if there is good monitoring data available," emphasises UFZ ecologist Dr Dirk Schmeller.
State-of-the-art methods enable ecologists to use such information to obtain a fairly accurate picture of biological diversity and how it is changing. To this end, they observe various facets of biodiversity, such as the size of populations, the characteristics of species or the functioning of ecosystems and analyse how they change. To be able to obtain meaningful results, however, they need adequate data harvested over long periods of time. After all, they are only able to put a realistic figure on the loss of diversity and the role of humans by comparing different epochs: What was the world like before Homo sapiens transformed it completely? And what has changed since then?
The work by Dirk Schmeller and his British, French and Spanish colleagues now poses the question as to whether the monitoring programmes, which were launched only recently in most cases, can provide sufficient information. After all, humans started exerting pressure on modern fauna and flora and permanently altering them centuries ago. "In contrast, changes in society, such as more leisure time, higher environmental awareness and better education only comparatively recently brought about a situation where biodiversity data is being collected in a systematic way," the researcher explains. Is it therefore possible to use the information available to discern the consequences for biodiversity of the industrial revolution in the 19th century or the massive changes in agriculture since the 18th century?
In order to get a better assessment, Dirk Schmeller and his colleagues scrutinised for the first time the timeframe of European monitoring programmes. For this purpose, they consulted primarily the DaEuMon online database, which contains detailed information on the various monitoring programmes throughout Europe. It reveals, for instance, which methods are (or were) used to record data on which species in which countries. They additionally analysed information from other publicly accessible databases.
Even centuries ago, hunters, amateur naturalists and other enthusiasts began keeping records on the diversity of life. In this way, Dirk Schmeller and his colleagues came across studies on birds and plants dating from 1634, while the information on mammals even goes back just under a hundred years more than that. "There were no systematic data collections back then, however," the researcher explains. Instead, observers noted information on certain species in a rather arbitrary way and mostly limited themselves to relatively small areas and specific regions. In Great Britain, for example, there is a long tradition of birdwatching so that more is known about the history of the feathered inhabitants of the British Isles than about their relatives in other parts of Europe. This means that old data can provide only a very incomplete picture of the past diversity of the continent.
It is not until the second half of the 20th century that better information becomes available. Around 88 percent of European monitoring programmes were not kicked off until sometime after 1950. Just under half did not become operational until the beginning of the 1990s when the EU's Habitats Directive placed obligations on its member states to collect such data. But by that time Europe's ecosystems had already been under massive pressure for a long time. This is revealed by the history of human impact that the research team analysed and compared to the timeframe of the monitoring programmes as part of its study. Whether population growth or the emission of greenhouse gases, overfertilisation or pollution: all these issues have their origins long before the boom in monitoring.
Dirk Schmeller summarises: "As a consequence, we lack the correct baseline for all comparisons." People who are interested in the decline in the diversity of insects, for example, can indeed look back a few decades into the past. But they might then see only a fraction of the actual loss. They will find out little or nothing of all those species that were already unable to cope with the industrial revolution or the rapid changes in agriculture in the 18th century. "This means we are likely to massively underestimate the human impact," says Dirk Schmeller. This has far-reaching consequences. For example, when it comes to setting targets for nature conservation. It would appear to easily make sense if the objective is to preserve all bird and reptile species typical for a given area. The only question here is how to define "all". The list of species from the first instance of monitoring is, in all probability, incomplete, even if it does date back to the 1950s. Large numbers of the region's inhabitants were probably already long gone even by that stage.
Dirk Schmeller and his colleagues therefore argue that other sources of information should also be tapped in order to be able to look further back into the past. Firstly, they identify possibilities from a systematic evaluation of the extensive collections brought together by museums worldwide. "Secondly, palaeobiology can also supply very useful information," states Dirk Schmeller. This discipline attempts to reconstruct landscapes and ecosystems that have long disappeared. As an example, by drilling deep down into lake beds, researchers obtain sediment cores that can be examined for ancient pollen, seeds and microorganisms. More information on the biological diversity of bygone ages can also be found in fossils and old DNA. "These methods can be used to look back thousands of years," says Dirk Schmeller. "But we would content ourselves with as little as 250 years in order to be able to understand modern fauna and flora."
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More information: Jean-Baptiste Mihoub et al. Setting temporal baselines for biodiversity: the limits of available monitoring data for capturing the full impact of anthropogenic pressures, Scientific Reports (2017). DOI: 10.1038/srep41591
Neil Brummitt et al. Taking stock of nature: Essential biodiversity variables explained, Biological Conservation (2016). DOI: 10.1016/j.biocon.2016.09.006