• Ilkka Hanskin Luontoverkko

Why protected area networks are networks?

Päivitetty: elo 22

Humans alter nature in many ways. The ongoing global-scale modification of natural habitats has pushed populations of many species in decline, and species are going extinct at an alarming rate. One of the oldest and most effective ways of halting extinctions and biodiversity loss is to protect areas: by preventing human presence and activities, we allow other species to survive in these areas.

Protected areas have a long-history. Already during middle ages, it wasn’t uncommon for rulers and the wealthier members of the society to preserve parts of their lands as hunting grounds. Access to these areas was forbidden from the common folk, which sustained higher populations of game species so that landowners could hunt at their leisure. In the Western culture, the era of modern conservation is often said to have started in 1872 with the establishment of Yellowstone National Park in the United States of America. This was one of the first protected areas in the Western world with the objective of preserving natural values for generations to come. It is perhaps worth reminding though that the Yellowstone National Park was established by the white government of the United States and covered areas that had been inhabited by several Native American tribes for over 11,000 years, and who were consequently driven out from their lands.

Today, approximately 15% of Earth’s terrestrial surface and 7.5% of oceans are protected under various conservation laws[1]. The global coverage of protected areas can be seen as modest, given that many of these protected areas are located in remote, less productive and economically less valuable regions, which are not necessarily the most biodiversity rich of all places. This skewed placement of protected areas can also be seen in Finland, where around 20% of Northern Finland is currently protected, while in the more densely populated and more biodiverse Southern Finland protected areas cover a mere 5% of the region.

Photo 1. Mesic black alder forests are rare in Finland, and usually found as small patches on wetlands and along coastal and lake shores. But why do we always talk about protected area networks? Couldn’t we just set aside a single large area for nature, leaving rest of the land and water for human use?

Networks are needed to capture the highly diverse, and patchy, dimensions of life

The most obvious reason for the need of several protected areas is that species and habitats simply have different distributions. Ecological communities, formed by the species present in a region, change entirely when moving between major climatic zones. For example, in Finland the northern fauna and flora communities are in many parts different from those in Southern Finland and many species can only be found either on the very northern or southern tip of the country. Through evolution, all species have also specialised to live in different habitat types, such as forests, wetlands and meadows. These rarely occur in single continuous areas but typically form mosaics of various complexity within a region. Even species inhabiting the same habitat type may have differing distribution patterns because, in addition to available habitat, their distributions are shaped by complex biotic interactions with other species, such as predation, parasitisation and competition. In order to protect as many species as possible, a network of protected areas is therefore needed.

But it is good to be aware that the distributions of species themselves can also have a network structure. In books and maps, species distributions are often displayed as continuous areas, but these only show the extreme limits of species ranges beyond which they are not found. In reality, the distributions of many species are formed by several separate populations located in high quality habitat areas where there are plenty of resources for individuals to survive and reproduce. Areas between these core populations can have varying roles. They can be important for the movement of individuals, support smaller marginal populations or simply have no value for the particular species. In many regions, human activities, such as building roads and buildings or converting natural vegetation to farmlands, have further fragmented previously continuous habitat patches into several smaller fragments.

Building networks of protected areas is not just a smart strategy, it’s also a necessity

Because governments around the world allocate only small amounts of money for conservation, the scarce resources need to be spent as cost-efficiently as possible. From purely strategic perspective, it’s worth to have a species protected on multiple protected areas: this reduces the risk of losing the last remaining population to events such as wildfires or diseases. One of the main goals of conservation planning is to identify those areas that together capture the core populations of as many species as possible. This is no trivial task, keeping in mind that there are 48,000 species in Finland alone, and more found regularly[2]. For this reason, researchers at the University of Helsinki have developed computer software that utilise highly efficient algorithms that can analyse distribution maps of several thousand of species and identify those locations that together capture the core areas of all species. These methods are currently used, for example, to guide the designation of the protected areas in the Finnish METSO forest conservation programme[3].

Photo 2. Each species has their own habitat requirements. These are determined by, among other things, the size of their territories, movement needs and the availability of resources.

But building successful protected area networks requires more than just getting parts of all species’ distributions protected. As natural environments outside protected areas keep degrading and disappearing, populations inside protected areas are also affected. Population ecology and particularly metapopulation ecology, which Ilkka Hanski researched, have taught us that species cannot necessarily be saved from extinctions simply by protecting their core populations. When designing protected area networks, particular attention need to be given to the structure of the network. Among other things, movement of individuals between protected sites need to be secured so that the genetic diversity of populations remains healthy. Also, smaller marginal populations have been shown to have important roles in supporting species persistence: they support larger population sizes in the core locations and speed up their recovery from natural population fluctuations.

We are getting good at building protected area networks but there is still lots to learn

Integrating this ecological knowledge into conservation planning practices has, however, turned out to be very challenging. Because of the immense diversity of species and their ecological needs, a network design best suited for one species rarely meets the needs of another species. One of the long-lasting unresolved questions in conservation planning is how the structure of protected areas networks or even individual areas should be configured. Is it better to have only few larger areas that are less sensitive to external disturbances, or should we opt for several smaller areas that might allow more species to be protected and to better support their population dynamics? So far, we haven’t been able to identify those critical characteristics of a network structure that would support the long-term persistence of all species, from small insects to large mammals and trees. As habitats outside continue disappearing, the coverage and structure of protected areas plays increasingly larger role in the effectiveness of conservation actions.

Climate change poses additional threats, as it can make local climates inside protected areas unsuitable for species and force them to move to new regions. While central to protecting currently important locations for biodiversity, protected area networks also have an increasingly important role in helping species to adapt to the changing climate and to disperse to new regions. The Ilkka Hanski Nature Network is a stellar example of a protected area network with an object to protect a broad range of biodiversity in a human dominated landscape. Currently, the network comprises of 11 areas with a diversity of habitats that range from open rocky bird islands to boreal forests and marshlands. The network’s location at eastern Gulf of Finland brings together habitats and species of both continental and coastal climates, and many species expanding their ranges northwards with the changing climate have first found their way to Finland through this area.

Ever since the foundation of Yellowstone National Park, the science of conservation planning has advanced in great leaps. But there is still much to learn about how to design the most optimal network of protected areas that can secure the persistence of our biodiverse nature in the changing world.

Heini Kujala

University Researcher, Finnish Natural History Museum, University of Helsinki

Project Leader, NESP Threatened Species Recovery Hub

Honorary Senior Research Fellow, The University of Melbourne [1] https://www.protectedplanet.net/ [2] https://wilderness-society.org/the-golden-jackal-expands-to-finland/ [3] https://www.syke.fi/en-US/Research__Development/Nature/Specialist_work/Zonation_in_Finland

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