Connectivity of the global network of protected areas

Luca Santini, Santiago Saura & Carlo Rondinini.

Aim
Millennia of human activity have drastically shaped the Earth’s surface confining wildlife in ever more rare and sparse habitat fragments. Within the strategic Plan for Biodiversity 2011–2020, Aichi Target 11 aims at the expansion of the current protected area (PA) system and the maintenance and improvement of its connectivity. This study aims at providing the first overview of the functionality of the PA networks across the six continents at different dispersal distances relevant for terrestrial mammals.

Location
Global.

Methods
We used a graph theory approach to assess the connectivity of PA networks of different continents across a wide range of dispersal distances. We assessed the connectivity of country-level PA networks, the connectivity of con- tinental PA networks and the contribution of country-level PA networks to continental connectivity.
Results National and continental networks are characterized by very different spatial arrangements that translate into different levels of connectivity, ranging from networks where the reachable area is mostly determined by structural connectivity within PAs (e.g. Africa) to networks where connectivity mostly depends on animal dispersal among PAs (e.g. Europe). PA size correlates positively with connectivity for all species, followed by PA number; dispersal contributes less and positively interacts with number of PAs.

Main conclusions
Continental networks perform worse than national networks. Transboundary connectivity is often weak and should be improved, especially for countries that are important in promoting continental connectivity. Increasing PA coverage and size is a good strategy to improve multispecies connectivity.

figure-1-percentage-of-reachable-area-ecanorm-for-the-protected-area-networks-within

Percentage of reachable area (ECAnorm) for the protected area networks within world countries. (a) represents ECAnorm for the lowest dispersal distance considered (177 m). (b) represents the difference in ECAnorm between the lowest and the maximum dispersal distance considered (99.58 km), thus indicating the sensitivity to dispersal distance of each country’s network.

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