Biodiversity informatics < Threat synopsis > Concluding remarks

5.2 — Threat synopsis

Integrated species information systems will allow "data mining that cannot be imagined today" (Edwards et al. 2000). But, as outlined above, there might pass considerable time until these systems will provide all available data with the necessary high spatial resolution needed for efficient planning. Meanwhile, we have to continue with a fuzzy decision approach, which is intuitively followed already by many conservationists. The alarming situation of many migratory species has been outlined, and the major threats are well-known. One does not require huge data sets or sophisticated GIS-analysis to see the disastrous consequences of habitat destruction, pollution, or bycatch by large-scale fisheries. Examples have been presented in the previous chapters, and for individual species within Annex II. The principal threats affecting whole species groups are summarised in Table 5.1.

Tab. 5.1:

Cross table for major threats and species groups. "Y" signifies an important threat for the respective group; for details see the respective sections.

EP: Environmental pollution,
AL: agriculture – land conversion,
F: Forestry,
WL: wetland loss,
C: construction,
C-dams: river dams,
FD: fishery – direct,
FI: fishery – indirect,
H: hunting.

Tab. 5.1:

Kreuztabelle wichtiger Gefährdungsfaktoren und den betroffenen Tiergruppen. "Y" bedeutet einen beträchtlichen Einfluß des Gefährdungsfaktors auf die Tiergruppe; nähere Beschreibungen und Beispiele findet man in den entsprechenden speziellen Kapiteln sowie in den Legenden des Annex II.

EP: Umweltverschmutzung,
AL: Landwirtschaft – Landumwandlung,
F: Forstwirtschaft,
WL: Verlust von Feuchtgebieten,
C: Bautätigkeit,
C-dams: Staudämme,
FD: Fischerei – direkt,
FI: Fischerei – indirekt,
H: Jagd.

Animal Group
  Habitat conversion Taking
  EP AL F WL C C-dams H FD FI
Bats Y Y Y   Y        
Seals Y         Y Y   Y
Terrestrial mammals   Y Y   Y   Y    
Whales and Dolphins Y         Y   Y Y
Bee-eaters, rollers, kingfishers Y Y Y   Y   Y    
Cuckoos Y Y Y            
Hoopoes Y Y              
Nightjars Y Y Y            
Owls Y Y Y   Y   Y    
Pheasants, bustards, sandgrouses, buttonquails Y Y     Y   Y    
Pigeons Y Y Y       Y    
Plovers, lapwings, snipes Y Y Y Y Y Y Y    
Raptors Y Y Y   Y   Y    
Seabirds Y     (Y)   Y     Y
Songbirds Y Y Y Y Y   Y    
Swifts and Hummingbirds Y Y Y   Y        
Waterbirds Y Y   Y Y Y Y    
Woodpeckers Y Y Y            
Turtles, crocodiles Y     Y Y Y Y Y Y
Fishes Y   Y Y Y Y   Y Y
Invertebrates Y Y Y Y       Y Y

The most severe threats can be summarised as follows:

Environmental pollution

Herbicide and pesticide use, either for agriculture or for disease control, remains a major threat to practically all groups of migrants. While the use of DDT has been successfully suppressed, other pesticides continue to accumulate within the food chains. Together with organochlorine phosphates, PCBs and a wide variety of other chemical substances, they now can be detected even in pristine ecosystems, such as the Arctic or the Antarctica. Top predators such as seals, whales and dolphins, raptors and certain fish species accumulate huge amounts of chemicals, depending on the regions and their prey. Amazon fish species accumulate mercury from gold mining, and whale meat has such high concentrations of chemicals that it should be forbidden for human consumption. The "International Council for the Exploration of the Sea" ( offers a database of toxic substances found in marine organisms. It demonstrates the impressive variety of chemicals involved, and species affected. It is evident that a successful prevention of chemical pollution, including chemical catastrophes, is extremely important for long-term conservation of most migratory species.

Agriculture land conversion

Because most migrants occupy large areas, they necessarily use agroecosystems at least during part of their life cycle. Many species have adapted remarkably well to traditionally managed areas. But this dependency makes these species particularly sensitive even to apparently small changes in agricultural practice. Most collapses of European bird populations are due to such changes, which have been well studied. They can be remedied remarkably well by extensivation programs, as for the corncrake in England and the Netherlands. Huge problems have to be solved on a global level, due to the rise of new crops and new techniques. Massive changes must be expected from the extension of the European community, and the unavoidable overall extension of agricultural areas. The conflict between wild animals and agriculture will therefore gain importance, and will be among the most difficult challenges to conservationists.

Wetland loss

Rivers and wetlands are under severe threat by increasing demand for water, pollution of water catchment areas and drainage. Wetlands are important key habitats not only for waterbirds, but also for many other bird species and fishes. Mangroves in particular have been transformed at an alarming rate within the last decade, which severely affects marine habitats and species. Booming shrimp aquacultures converted most mangrove habitats in southern East Asia, Ecuador, Central America and parts of Africa in not much more than a decade. Even remote areas have been totally transformed, and probably have affected fish species, turtles, waterbirds and seabirds directly or indirectly (Hardtke 1998).

Dam construction

River dams have led to the immediate collapse of the respective diadromous fish populations. This includes economically important species such as salmon or sturgeon, and led to the breakdown of local fisheries. In addition, freshwater dolphins and some marine mammals with inshore migration (including manatees) are severely affected. Additional effects include the alteration of the entire watershed including wetland complexes and deltas due to upstream and downstream changes of riverbeds,

increased sediment load and higher salinity due to evaporation: one third of the Colorado river flow (Mexico, US) evaporates from reservoirs (McCully 1998). Existing and planned dams often have pharaonic dimensions, and impacts are probably irreversible. The "Three Gorges Dam" (Yangtse, China) is now under construction, and will affect the staging areas of the Siberian crane (Figure A2.45). The huge investments for dam construction in "third world countries" are only possible by international funding from multilateral development banks and export credit agencies (e.g. World Bank, European Development Fund; for an extended list see McCully 1998 (Table 9.2) and World Commission on Dams,


Hunting has been the cause for complete or nearby extinction for several migratory species, such as the passenger pigeon (Ectopistes migratorius). Some other species became exterminated without leaving traces of their possible migratory behaviour, such as Steller’s seacow or the great alk. Hunting is still a severe problem in some parts of the world, such as the hunt for houbara bustard (Chlamydotis undulata) in the middle east (see Figure A2.68). The recent shooting of satellite-tracked birds in France and Germany demonstrates the inadequacy of control, even within CMS member states with highly regulated hunting schemes. Among the shot species were several listed on CMS Appendices, such as a black stork (Ciconia nigra; Appendix II), or the threatened lesser white-fronted goose (Anser erythropus; Appendices I and II), shot at a protected site in Germany (Øien & Aarvak 2001). Though the time and localities of shooting could be identified with high precision, and both cases raised considerable publicity, there was no legal persecution in any of the cases.

Fishery – direct and indirect

Fishery is the most direct and massive way of "taking". Whaling should be included here, because of the strong overlap with respect to habitat and main actors. Though there are extensive legislative frameworks and quotas, fishing is a direct form of massive non-sustainable exploitation. Several once abundant fish stocks collapsed, and with them whole regional economies. Besides the direct threat of the target species, depletion of marine species affects entire marine food webs, and top predators such as marine mammals or seabirds. Whaling is a highly political issue, mainly debated within other international agreements such as IWC and CITES. Memoranda of Understanding and "further research" will not be sufficient to solve these problems, and it is recommended that CMS instruments and legislative frameworks be extended by executive and efficient control instruments, such as the employment of fishery observers or test cases at court.

Finally, global change will severely affect a considerable number of migratory species. This new threat is difficult to measure, predict and to combat. Emerging problems cannot be solved directly. However, the following recommendations should be considered, to minimise catastrophes and species extinction risks:

  1. large populations are necessary to provide the genetic diversity for the necessary adaptation to a changing environment,
  2. maintenance of entire species ranges and potential habitats are necessary, to allow for adaptive changes in migration patterns,
  3. hunting and taking must be reduced, as their effect will be more severe on weakened or concentrated populations.
Biodiversity informatics < Threat synopsis > Concluding remarks

This document should be quoted as part of the publication "Riede, K. (2001): The Global Register of Migratory Species ­ Database, GIS Maps and Threat Analysis. Münster (Landwirtschaftsverlag), 400 pp." + CD

 by Klaus Riede