Ch. 12 Managing Ecosystems

Modified Ecosystems Most (all?) ecosystems have some detectable amount of human influence. We will focus on semi-natural ecosystems managed for extraction

Forestry Most forests are not in reserves, or in reserves where logging is allowed Age structure: even or uneven aged stands even-aged: Landscapes with even-aged stands of many ages uneven-aged stands: maintain diversity of ages at the landscape level, both uneven aged stands and even aged stands of different ages Ideal harvest is earlier than natural tree death -> few old trees Dead wood is important nurse logs for seedlings, providing nutrients and water habitat and food for insects, habitat and foraging for woodpeckers

Resolving Age-Structure Problems Allow some trees to age an dies small-scale: identify trees to be left uncut mid-scale: leave uncut patch in every cut patch, avoid cutting near riparian areas larger-scale: avoid a few old trees during clear-cut very large-scale: setting aside entire forest as protected area Defer cutting especially for even-aged stands allows trees to provide habitat for that many more years Silviculture, artificial selection to increase growth Girdling trees to provide dead wood

More Forestry Spatial Patterns: Gap dynamics, cycle of succession in an opening created by downed tree, important in forests Important to match the scale of cutting to the scale of natural disturbance range from cutting a few select trees to entire stands small-scale cutting not always preferable to large-scale Species compositions: not all timber is equally valuable may replant with preferred or exotic species

Livestock Grazing 25% of land-surface is rangeland of some sort. Ideally, domesticated grazer would be similar to native grazers some grazers used primarily in their native range growing interest in growing native grazers for meat Mimic natural grazing patterns rotate herds among pastures heads/acre Beware of overgrazing -> desertification Natural disturbances: fire, flood, drought, wind Predators: can be managed by guarding herds, removing problem individuals Competitors: for forage, or disrupt soil “Improved” pastures: introduce palatable exotic grasses

Fisheries Potential to profoundly modify ecosystems by altering food web Many fishing ground publically owned, requires regulation Goal is to manage sustainable harvest difficulty in regulation makes this complicated Mismatch with natural fish mortality Allies: Oppose pollution, dams, wetland degradation Enemies: introduce species, remove natives

Extractive Reserves Intrusive or large-scale activities forbidden commercial logging large-scale agriculture Subsistence and limited extraction permitted nut and fruit collection subsistence fishing Conservation is a secondary goal

Ecological Management Manage ecosystems so that human disturbance mimics natural disturbance as much as possible

Cultivated Ecosystems Agricultural fields, orchards, tree plantations, aquaculture, etc Tree plantation vs. intensely managed forest? Conversion from natural to cultivated ecosystems in the primary cause of biodiversity loss Tend to be ignored in conservation, but can be managed to ameliorate biodiversity loss can be managed to ameliorate impacts to surrounding areas

Biodiversity in Cultivated Ecosystems Relicts of intact habitat critical for biodiversity preservation not big enough to require separate management, but act as refugia for species hedgerows, ponds, hammocks mesofilter Predator and pest control Timing of tilling, mowing An ecosystem worthy of conservation in its own right?

Minimizing Negative Effects of Cultivated Ecosystems Integrated pest management: uses natural enemies of pests, mixing of crops, and conservative use of chemicals Many species thrive around agricultural areas, not always a good thing GMOs: increase crop production, risk escape of mutants suitable buffer between natural and developed lands

Economic Perspective Subsidizing practices that maximize biodiversity Conservation easements landowner keeps land, continues using it, but sells development rights

Triad Approach to land-use allocation Three types of land use Cultivation with high production of commodities Protection with no commodity production modified ecosystems with commodity production while maintaining ecology In Maine, intensive forestry produces 4x as much as extensive; for every hectare switched from extensive to intensive, you can put four in reserves, with no change in production move to intensive, preserve output? reduce extensive, reduce consumption?

Built Ecosystems Cities, factories mines, highways Human structures dominate, but species persist Human habitat: increasingly urban, leaves more room for natural areas elsewhere Biodiversity: you’d be surprised, but may differ from other pops. Import energy and food, export pollution, usually via water Urban planning can increase biodiversity and reduce impacts city parks yards and gardens cemeteries golf courses

Restoring Ecosystems Humans have been degrading ecosystems for thousands of years, but we can also hasten their recovery Protecting can only save what we have, restoration can give us more area to work with. Mitigation of development place on already degraded site, restore after use is complete, restore nearby site, protect nearby natural area

6 Steps in Restoration Set a goal. Find a reference site to use as a target/template. Determine strategy/methods. Ecosystems are incredibly complex, will need multi-pronged approach. Remove source of degradation. Restore physical environment. Substrates, hydrology, fire, etc Restore biota. Translocation, planting, or wait for dispersers Be patient. Keep monitoring.

Problem with restoration Idea that we can “fix” degraded ecosystems is attractive used to justify degradation (we can fix it later, no harm, no foul) That idea also incorrect we might be able to restore an ecosystem, but will it ever be exactly the same? costs of restoration probability of failure

Discussion Qs You have a semi-natural forest. Would you convert half to plantation if the other half was made a protected reserve? Should biodiversity initiatives in urban areas be funded by state or municipal government, or federally funded? Should exotics be used in restoration? Under what conditions?