South African park managers ask the question: how to we manage for ecosystem heterogeneity in a landscape of fences.
Elephant numbers in Kruger. Culling ended in 1994 (numbers around 9000). Now numbers are 16,000 and continuing to soar. Are these elephants making the landscape more homogeneous or heterogeneous?
They “tag” and monitor millions of trees, using airborne lidar (3D tree structure) and spectroscopy (tree species)
Stunning 3D fly through over area with elephants (few trees) and areas with elephants excluded (many trees). Browsers have it tough in one regime, grazers in the other.
There is a strong abiotic template. High fertility basalts on east, low fertility granites on the west. There is also a finer-scale catena linked to micro topography. More woody vegetation high on crests (Levick et al 2010 Nature Comm). Regional precipitation gradient from very dry in the north and fairly wet in the south. Woody vegetation is in low areas in the north, in uplands in the south. So need to be careful of abiotic heterogeneity.
Various types of exclude. Either all animals large than a hare, or only elephants and giraffes.
Background tree fall rate in exclosures increases with rainfall. Tree fall rates change by up to TWO ORDERS OF MAGNITUDE in the presence of elephants. (Asner and Levick 2012 Ecology Letters). IN these exclusres, tree number loss is strongest in the height range 5-8 metres - this is an “elephant trap”
Shows map of processes. Woody encroachment in background as well and elephant knock-down. Massive loss of Acacias. Park-wide changes in canopy height. There is some growth but it is trumped by losses. They assess if the change in fire regimes would affect tree fall rates. Less than 10% of tree fall in the park can be attributed to fire. The fire programme has had little impact on woody vegetation.
Question: there is a strong focus on outcomes and states in Kruger rather than processes (as pointed by Monbiot). Kruger is fenced. One key process in movement. How much of what we see is a result of confinement by fences or fear of poachers? Is this an unnatural system?
Elephant numbers in Kruger. Culling ended in 1994 (numbers around 9000). Now numbers are 16,000 and continuing to soar. Are these elephants making the landscape more homogeneous or heterogeneous?
They “tag” and monitor millions of trees, using airborne lidar (3D tree structure) and spectroscopy (tree species)
Stunning 3D fly through over area with elephants (few trees) and areas with elephants excluded (many trees). Browsers have it tough in one regime, grazers in the other.
There is a strong abiotic template. High fertility basalts on east, low fertility granites on the west. There is also a finer-scale catena linked to micro topography. More woody vegetation high on crests (Levick et al 2010 Nature Comm). Regional precipitation gradient from very dry in the north and fairly wet in the south. Woody vegetation is in low areas in the north, in uplands in the south. So need to be careful of abiotic heterogeneity.
Various types of exclude. Either all animals large than a hare, or only elephants and giraffes.
Background tree fall rate in exclosures increases with rainfall. Tree fall rates change by up to TWO ORDERS OF MAGNITUDE in the presence of elephants. (Asner and Levick 2012 Ecology Letters). IN these exclusres, tree number loss is strongest in the height range 5-8 metres - this is an “elephant trap”
Shows map of processes. Woody encroachment in background as well and elephant knock-down. Massive loss of Acacias. Park-wide changes in canopy height. There is some growth but it is trumped by losses. They assess if the change in fire regimes would affect tree fall rates. Less than 10% of tree fall in the park can be attributed to fire. The fire programme has had little impact on woody vegetation.
Question: there is a strong focus on outcomes and states in Kruger rather than processes (as pointed by Monbiot). Kruger is fenced. One key process in movement. How much of what we see is a result of confinement by fences or fear of poachers? Is this an unnatural system?