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Lecture 13

ENV334H1 Lecture 13: L13-Restoration

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University of Toronto St. George
School of Environment
Helene Cyr

Restoration Ecology: Ecosystem restoration, rehabilitation & reclamation March 13, 2017 Restoration Ecology • Bradshaw said this in the 80s: o Well and fine to try and understand communities, and ecosystems o But acid test for checking that we’re understanding any kind of process, is not that we can take ecosystems to bits of pieces of paper, but can we actually put a community together o Experiments of what can we achieve with all of the knowledge we’ve got • Ecological restoration o Movement that started in early 2000s o Process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed o A lot of material we can work with, but seldom have data Probability of Rapid and Full Ecological Restoration • Original ecosystem (green star) • Can think of disturbances both in terms of scale (how much of landscape was disturbed), and degree/intensity of disturbance • Small-scale disturbance that’s not to intense, then recovery rapid o Community will probably come back to what it was before o Size of circle = probability that system comes back • Fairly small-scale (spatial scale) but very intense = more difficult to come back to original state • Low intensity disturbance, but spans large proportion of landscape, then harder to come back from • If have large and severe disturbance, then system is unlikely to come back to original state o Or might take long time to recover Ecological Restoration • 3 different categories: [1] Restoration • Attempt to return ecosystem to historic condition • Recreate it in terms of species and function [2] Rehabilitation • Had change, but now conditions aren’t same as before • Can’t restore all of it to what it was before • Try to recreate some ecosystem processes (some of the function) but not aiming to make sure all the species are there • = Functional restoration • Won’t see same species • 1 step below full restoration [3] Reclamation • Such a degraded system that there’s no hope of even getting function back • Just want an ecosystem • Maybe just have a cover so soils don’t erode away • Might have to recreate a whole new ecosystem • 3 levels of restoration that mean you’re going back (or not) to some state Diagnose Damage • Start with fully functionally intact system • Then some kind of stress or disturbance o Community changed to sthg really different maybe that wasn’t functional o Along the way might have lost a lot of species • Biotic threshold: Which species are there? How has it changed • Abiotic threshold: Maybe physical chemical characteristics of site have actually changed o Left with very degraded community • Is it possible to get from state 6 back to state 1? [1] Rehabilitation: o Take state 6, and try to raise abiotic threshold or site so that can get some things back o Get some abiotic conditions so that some organisms can live there that can re-establish some sort of function o But can’t go back to all the characteristics (all the species) or original conditions ▪ i.e. can’t get back to state 1 [2] Restoration o Trying to get back all of your species [3] Reclamation o Very degraded o Try to establish some organisms/function but nowhere close to original Need Clear Goals • If no goals, then won’t know where you’re going • What you should measure to try to convince people that you achieved something • Involving people to decide • Restoring to what state? o How far back in past do we want to restore this community to? ▪ Communities aren’t static ▪ Environmental conditions have changed over thousands and thousands of years o Is that state we want still viable? ▪ Might have had changes (climate change, hydrology because of diff constructions) ▪ Might not have abiotic conditions to have those organisms ▪ Need to figure out what we can actually restore to • Restoring what? o Species ▪ Most projects want to restore all species that were there (biodiversity) o Ecosystem functions ▪ Select certain ones o Ecosystem services ▪ In general though, services come from function ▪ Just that the public doesn’t know what function is Ecosystem Services • 4 different services • More for communication with public • EAsier for government to communicate with public if speak in terms of services rather than ‘function’ [1] Supporting • Primary production o Food for food web o Nutrient cycling [2] Provisioning • What can we harvest and get out of ecosystems • Fish, timber, fodder [3] Regulating • Ecosystem process that makes ecosystem • EX: Herbivores/predators/biotic interactions, C sequestration, water supply (quality and quantity of water), soil characteristics, pollination [4] Cultural • Esthetic values Why is Biological Diversity Important? • Implicit relationship between diversity of community and its function in ecosystem (how it makes ecosystem function) • Asking why we care about biodiversity (why does it matter if there’s 100 or 50 spp) • General idea that ↑ diversity = ↑ function • But probably not a straight line o More of a plateauing line o If increase biodiversity, will get more function (primary production, nutrient cycling) o But eventually don’t get more function even if increase biodiversity • If interested in effect of reducing biological diversity, how will this affect ecosystems? o Species could be redundant • 3 different hypotheses that are closely related [1] Redundancy hypothesis • People think that it means we can lose some species and it’s okay • If went down in terms of biological species, tell us what number we should have to cover all the functions • But probably not the same species that will do that function • Some species better under certain conditions • EX: Have a few species doing N fixation (all same function) o But some might do better in dry years and some better in wet years o So still need all the species to provide insurance hypothesis [2] Insurance hypothesis • Species are redundant but don’t perform in same way [3] Rivet hypothesis • Species like rivets on plane • Thousands of rivets on plane • All hold plane together • If lost one rivet on airplane is okay • If 12 might still be okay • But might lose so many that plane crashes and won’t be able to fly • As losing diversity, maybe is somewhere where you fall off • 3 hypotheses that are all linked together • Function increases in non-linear way with biological diversity • But we also think that curve isn’t a straight line • Depends on which species we lose first • If lose species, might be okay for a little, but eventually, function will decline • Depending on which species lose first (maybe was keystone) could lose function quickly • = Bottom boundary of blue area • Or maybe no keystone species, and only when you lose that particular species, system falls apart (top boundary) • Many possible routes • Relationship between having species • If can recover species, will recover ecosystem function How to Restore • Different steps to be taken [1] Impact • What was the impact on that particular area? • Maybe was some change in community composition or architecture [2] General Cause [3] Intervention • Differential site availability o If there isn’t as much site available as before, then need to fix site: o Remove disturbance o Fix site • Differential species availability o Assisted dispersal • Differential species performance o Species aren’t performing properly o Need to adjust either physical/chemical conditions of site o i.e. maybe pH too high or too low o Invasive species • Causes determine interventions General Restoration Principles • Give general guidelines, but once you have specific project, need to adapt • All of the points go from restoring locally, to restoring to larger and larger scales • Trying to make large area self-sustaining • First steps would be to restore environment to restore population itself: o Want self-reproducing populations o Not only is environment there but can reproduce and maintain itself • Need to reduce threats o EX: Reduce air pollution • Then use assemblages of species characteristic to reference ecosystem that provide structure o Should use native species when possible o Sometimes native species not used: ▪ If losing soils quickly and natives grow slowly ▪ Natives might not establish fast enough ▪ Just need non-natives to stabilize soil o Try to include all functional groups ▪ Idea of redundancy ▪ Have choice of different species we can have ▪ Want to restore ecosystem functions to what was there before • Eventually have self-sustaining ecosystem o As something that is self-functioning and that can resist/be resilient to periodic stress (dry/wet year) o Eventually work at landscape scale ▪ i.e. If have self-sustaining ecosystem, now want to try to reconnect to whole landscape o Try to work in larger and larger scale and try to get back to what was there before Setting SMART Goals • Need clear goals that you can monitor so that you know you were successful • Specific • Measure • Achievable • Reasonable o Given funding, time, resources • Time-bound o Over specific time-bound • If have all of this, then can follow what happens after you’ve done restoration • Show that what you did has an effect Monitoring and Evaluating Recovery • Might have degraded site for which we have no previous data on • Need to find reference site o Site that is as similar as possible but hasn’t received particular disturbance ▪ EX: Around Sudbury area, have a lot of acid rain and have a lot of degraded state ▪ Won’t find reference site that’s right in Sudbury ▪ Need lakes of similar geography, similar rock composition o Could also have more than 1 reference site o Gather information on degraded site + reference sites • Plan ACTION sometime down the line o Maybe for a while not doing restoration, but just monitoring o Where is that degraded site now compared to reference site o Then plan action for that time o How does that action affect degraded site? o If had done no action, might have gone some way o But hopefully, management will bring you back closer to reference site o If have different ways to restore, might have to plan restoration around different options o Some areas where have no actions • Why is the No Action and reference site important? o Say you have no reference site, and no action and management brings you up and you say “Oh Yay” o Why might that be not convincing? ▪ Increase in performance may be by chance ▪ Maybe was a good year by chance o No reference site/action site, don’t know Monitoring and Evaluating Recovery • Mana Island NZ: Suite of islands • Invaded late by Mauri’s (indigenous people) and then later by Europeans • Europeans started cutting trees for agriculture o Also brought in mammals • NZ was separated from Australia before mammals evolved • But Mauri’s and Europeans brought mammals • Ended up with a lot of big impacts from having mammals around • A lot of original diversity of islands linked to bird diversity o Many ground-nesting birds because no predators o But mammals changed community • Because the islands are small and isolated, was pretty easy to control the mammal populations o On Mana island, eradicated all the mice o If go to visit these islands, officials make sure you don’t have any animals • Then planned experiments: o Adaptive Management ▪ Had reference site • = original forest ▪ Had areas that were disturbed that they wanted to restore by planting native plants ▪ Some places where didn’t take any action • Kept some areas where didn’t do anything (no action) then other areas where they did monitor o Compare areas of no action to plantings ▪ Are we getting anywhere close to reference site? Example 2: Restoration of Tallgrass Prairies • When got to prairies, was grass there already, very productive, really flat • So all of Midwest was turned into agriculture by Europeans • Turned into fields, less than 1% of original prairies left • In 1960s, people wanted to bring back tall-grass prairies with bison • But very little of this environment left for the bison • Neal Smith o Put resources to coordinate projects and build up large projects o Neal Smith Wildlife Refuge o Goal of refuge is to restore original tall-grass prairies that were in this area o Try to re-establish function and ecosystems • Problem: o Site has been farmed with fertilizer for long time o Soils too productive for native species ▪ Need soils to be less productive o Also no seeds available o = Small remnant areas, but need to gather seeds, grow them again, to amplify seed bank to start planting over large areas Restoration of Tallgrass Prairies • Try to get ecosystem back to what it was • Try to take several things you can measure • Prairies have a lot of organic carbon because roots or plants grow deep • At beginning of project • In remnant part of prairies, have some data o Can be used to set target • Should have ~50 mg/ha of OM • If get trend, can predict how many years before we reach target in terms of soil organic carbon o Useful to have target and then monitor after restoration to see if you’re approaching your target March 16, 2017 Restoration of Tallgrass Prairies • Trying to restore tallgrass ecosystems that were taken over when people moved west • Try to restore them to vegetation that was there before • Problems: soil too productive + loss of seeds • Restored as best they could o Tried to restore soil organic carbon o Higher in prairie than in agricultural field • Know that tallgrass prairie has organic carbon • As monitor how things change through time • Can get better timeline of whether it’s an achievable goal • Organic content of soil was going up Restoration of Tallgrass Prairies • Then can start reintroducing animals o Butterflies o Bison • Other targets: o Soil organic carbon o Sample soil in many different parts of reserve o Streams also important ▪ Streams integrate themselves across landscape ▪ Monitored nitrate in streams ▪ Under agricultural had high concentrations because of fertilizers ▪ Konza prairie (areas that are more native) have lower concentration • = get target from less-impacted area (reference) Responses to Restoration • 3 different models • Is that system coming back to original state? [1] Rubber band model [2] Hysteresis model (Alternative Stable States) [3] Humpty Dumpty model [1] Rubber Band model • Start with original ecosystem • Add some degree of stress o For a while system is okay o Eventually if enough stress, system gets degraded • In case of rubber band model: o If you pull it then release it, will come back o i.e. just remove stressor and system will come back • Most likely to occur when: o Abiotic conditions are quite uniform ▪ Haven’t had major change of abiotic system o Not strong disturbance ▪ Small-scale/intensity o Intact species pool ▪ When remove stress, species fairly easy come back with minimal intervention • Don’t have to do much to community • Degraded site, remove stressor, site comes back to original [2] Hysteresis model • Had change from original state to degraded • When trying to recover system have to remove a lot more stress before you get a response and return to the original state • = Even when we removed stress, system doesn’t go back • Have to remove more stress just to get back • Alternative Stable States o Ball = ecosystem o In original state is stable ▪ Can have some disturbance ▪ But if put enough stress/disturbance and bring it past certain point, then ball rolls to alternative stable state ▪ Will be stable on its own • = degraded state ▪ To come back to other community, have to remove a lot of stress to push ball back uphill so that it falls into basin attraction • Have to go much further in terms of management Ecosystems with Alternative Stable States may need aggressive management • Grasses that grow fairly slowly and eventually stabilize dune • Dune can withstand quite a bit of wind power • Usually dunes are on shores • But because sand is held down by roots of plants, dunes don’t move too much (i.e. sand doesn’t just all blow away) • Dune community can withstand quite a bit of wind • BUT if disturb it and kill vegetation (i.e. walk on the dune all the time) might turn into really degraded area that has almost no vegetation • To bring it back to vegetated community, need to stabilize sand • If some plants started trying to grow would get buried by sand storm if nothing holding sand • Any plant that germinates will just get buried • Need to keep down sand to allow regrowth around sand dune • Need to stabilize sand dunes but is a lot of work so that wind doesn’t move all the sand around and keep disturbance at bay until all the vegetation is back o Once you destroy community hard to come back Ecosystems with Alternative Stable States • Shallow waters o = quite a bit of light so plants growth throughout water column high o = weeded lake • Eutrophication is one of the factors that might actually prevent this o If in area that has an area, plants usually die in winter and regrow in the spring o Plants have to make it to surface to start growing o Algae grows faster, so if have nutrients in water then algae can shade out vascular plants (before plants can make it to the surface) o Vascular plants had roots in sediments that stabilized sediments o In shallow lake will have resuspension of sediments ▪ Block the light o System where never enough light for plants at bottom to grow to surface o Flipped system from one dominated by vegetation to one where have no vegetation because nothing holding things in place • Turbidity: o Increased turbidity = loss vegetation, then suddenly a lot of turbidity o Need to reduce turbidity and eutrophication down past point where it shifted so that vegetation can re-establish • Alternative states o Almost don’t see major shift coming o Difficult in terms of management o Turbidity + eutrophication increasing o But then get catastrophic shift to another state o Hard to bring it back • Path for degradation isn’t same as path for restoration = hysteresis Is Target Achieved? • If expect system to come back to original state: o Could set target there • As monitor through time, can see if system is going back towards target and whether it’s going to achieve the target • EX: Ore mine o Soil polluted o Couldn’t get original forest back but got some other tree to grow back o All of their sites came back • EX: Calcareous soils o Movement towards target but variability in how well different parts of system are restored o Have diverse communities in areas o As they’ve been restored from agriculture to grassland, different areas behave differently o If agriculture going on for long time, might be hard to go back Indications of divergence (i.e. not all the sites are restored) • Abiotic conditions weren’t fully restored • Dispersal limitation o Are there pools of potential colonizers? • Biological processes variable o Which other plants are there? o Competition, herbivory • Important to have a target, but might not expect it to fit really well Humpty Dumpty Model • When falls off wall, can’t put it back together • Original state to degraded • Can be some recovery, but can’t get original o Something novel • Usually when something major happens • Maybe don’t have same conditions before you fall off wall Is Target Achieved? • Set target but your end community never reaches it o Maybe because you wanted to get back to original and is not possible o Or if have alternative target that turns out to be unrealistic • Prairie potholes o When tried to restore vegetation o Agriculture all around ▪ Species pool has changed ▪ Environment has changed What we see may not tell the whole story • Through many forest, often put roads • Those roads get trampled quite severely = soil compaction along roads • When you abandon roads, things start re-growing • When cut road, go from grasses and forbs (short vegetation to trees o Degraded state o But can let nature reinvade (what we do with small disturbances) o Probably takes longer • Or can recontour side of mountain or whatever land to try to loosen soil to enhance restoration • But also need to look below ground o Compaction has changed soil characteristics: ▪ Higher bulk density ▪ Lower conductivity ▪ Lower OM ▪ Lower nitrogen • Processes in soil have not been restored compared to aboveground vegetation • So what we see is not necessarily the whole story in terms of ecosystem functioning Complication: Invasive Species • Need to monitor invasive species because change story (extra stressor on degraded community) • New Zealand: o Lot of invasive species o NZ split from Australia before mammals evolved so never had mammals o Is very far from closest other land mass o But have received quite a few species from people coming in at different times o Have +2000 naturalized plant species • = managing novel ecosystem • Interactions among invasive species can lead to surprises o A lot of connections • Invasive species = long-term o Easier in islands because isolated but on mainland hard to stop their spread Past species loss may have weakened communities • Tall canopy plants that have huge seeds • Seeds mostly bird dispersed • Loss of bird species = poor dispersal o Moa ▪ 10 ft tall, 500 lbs ▪ Exterminated within 100 years of Maori inhabiting the island • Community changes with species presence/absence Long-term effects of invasive species • Red deer are invasive o Graze heavily on vegetation which is already stressed by lower dispersal o Selectively browse on saplings o Changes forest composition • Other plants o Invaded and affect native plant community o Gorse: ▪ Often introduced and is a nitrogen fixer ▪ Once if gets in, provides good services (stabilizes ground and provide nursery for plants to grow) ▪ But inputs N into soil that didn’t have as much N ▪ Native plants that grew there before that didn’t need so much N get pushed out Management of Whitaker’s skink • Complications for native species management • Have this skink only found in NZ • Mostly places where you can find this skink is islands off shore • Most populations are on small islands • But only main ground population is Pukerua Bay in NZ • Trying to manage to save skink Complex Interactions Lead to Surprises • Several ways of managing remaining popu
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