Managing Ecosystems Sustainably (OCR A Level Biology)

• Sustainability is the ability of an ecosystem to maintain (or ideally increase) its biodiversity whilst simultaneously providing humans with the resources they need over a long period of time
• Humans, in the way that they set up and manage an ecosystem, are in control of whether that ecosystem is sustainable or not
  • The resource must be allowed sufficient time to replenish before being harvested so that it does not run out
  • No harm should be done to the ecosystem, its surrounding areas, or to species living within it
  • Practices that boost biodiversity are promoted
  • The long-term future of the ecosystem must be guaranteed

• Two examples of managed ecosystems for sustainability are commercial fishing and timber production

Commercial fishing

• The human appetite for fish and seafood is very high, and growing fast as the human population rises
• Fish is a lean and healthy meat source with good protein levels for growth
• Modern fishing fleets have technologically advanced systems that could if used irresponsibly, strip the oceans bare of the most desirable fish species in a matter of months
• Sustainable fishing means:
  • Leaving enough fish in the ocean
  • Protecting habitats and marine food webs that fish rely on
  • Human communities that catch and process fish can maintain their livelihoods

• Governmental regulation can be enforced by:
  • Establishing fishing quotas
  • Agreeing areas of the ocean where fishing is banned (eg. spawning grounds) and permitted (eg. within a country's territorial waters)
  • Regulating mesh size of nets (to allow undersized/juvenile fish to escape)
  • Limiting the size of the fishing fleet by issuing licenses
  • Inspecting the catch as a fishing boat returns to port
  • Banning certain practices eg. gillnets (static nets that catch anything that swims by, and the fish struggle and die in distress)
  • Promoting sustainable practices such as trolling (different to trawling) that reduces bycatch

• Nevertheless, a lot of commercial fishing is carried out illegally
  • There is a very wide area of ocean for the authorities to patrol
  • High demand and profit potential has made poachers more daring and willing to break the law

Measures to make commercial fishing more sustainable

Trolling uses hook-and-line and reduces bycatch and damage to the seabed

Timber Production

• Human demand for wood and timber products fluctuates
  • In the mid-20th century UK forests were reduced to 5 % of the land area; today it's back up to around 12 % through afforestation efforts
• Timber remains an important resource in today's society, with many uses
• There is pressure on natural woodland to be felled and used as grazing land or for crop production, particularly in developing countries
• There are 2 main groups of tree crops used in commercial logging
  • Fast-growing conifers, e.g. spruce, pine, fir, larch
  • Slower-growing broad leaf trees, e.g. oak, beech, hazel

Fast-growing coniferous plantations

• Conifers are the fastest-growing trees in the northern hemisphere used as a strategic reserve of timber
• Low-grade agricultural land is used to grow these trees, creating an effective monoculture
  • Densely planted forests, deep shade, and needle litter at floor level all contribute to low biodiversity
• Work has been done to try and increase biodiversity in these areas
  • The use of felling methods other than clear-felling introduces pockets of variety into a plantation
  • Creation of clearings, firebreaks, selective felling, strip felling, edge habitat creation and in-situ leaving of naturally dead trees all attract other species and boost biodiversity
  • Genomic research has identified suitable sub-species, e.g. of Sitka spruce that can grow faster and shorten the tree breeding process
  • Recreation and public education projects now form part of the remit of forestry authorities

Coppicing and pollarding

• Coppicing and pollarding are felling techniques that can be used to sustainably manage slower growing broadleaf trees
• Coppicing involves felling trees close to the ground and leaving the stump of the tree in the ground; new shoots can grow from the stump and can be harvested again after around 7 years
  • Woodlands can be divided into regions and coppiced on rotation so that only small areas of the woodland will be lacking in mature growth at any one time
  • Coppicing means that trees remain relatively small and light can always reach the ground; this leads to more diverse woodland
• Pollarding is similar to coppicing but the trees are cut 2-3 metres above the ground, leaving the mature tree trunk in place
  • This brings many of the same benefits of coppicing but means that herbivores are less likely to be able to reach and consume the new shoots as they grow
• The timber produced by coppicing and pollarding is limited to use in smaller projects, e.g. fencing
  • The shoots that grow back after trees are cut in this way are long, thin branches; not one single stem
• Not all tree species are suitable for this type of management, e.g. very few conifers will grow back in this way after being coppiced or pollarded

Several woodland management techniques can be used to make commercial forestry more sustainable