S E Jorgensen, Copenhagen University, Copenhagen, Denmark © 2009 Elsevier B.V. All rights reserved.
Introduction How to Select and Apply Ecological Engineering
Ecological Principles Methods in Practice?
Thirty-Three Ecological Engineering Methods Further Reading
W. Mitsch and S. E. J0rgensen have published 19 basic ecological principles, which represent the ecological back ground as can be found in systems ecology of ecological engineering, in their book Ecological Engineering and Ecosystem Restoration. The principles will be repeated in this chapter in an abbreviated and slightly modified version, but a discus sion on how the ecological engineering methods presented in the parts Use of Natural and Semi natural Ecosystems to Solve Environmental Problems, Restoration of Ecosystems, Constructed Ecosystem - Imitation of Nature, and Application of Ecological Principles in Environmental Management are rooted in the 19 principles will be pre sented for each of the 19 principles. After the presentation of an ecological principle, the methods that are built on the application of the principle will be mentioned with an explanation of the relationship. Later, an overview of all the ecological engineering methods with reference to the principles on which they are based will be presented.
Principle 1: Forcing Functions Determine the Structure and Function of Ecosystems
This principle is actually the basis for ecological modeling, where a model gives the relationship between a set of forcing functions and the state variables for an ecosystem. The forcing functions are either natural forcing functions as for instance the meteorological conditions or man con trolled forcing functions as for instance discharge of waste water to a lake. Several ecological engineering methods change the forcing functions, particularly the man con trolled forcing functions. It is for instance clearly the idea behind the use of buffer zones (see chapter Buffer Zones) and natural or constructed ecosystems (chapter Natural Wetlands and part Constructed Ecosystem - Imitation of Nature) applied to reduce forcing functions with an
* Mitsch W J and J0rgensen S E (2009) Ecological Design Principles. In: Ecological Engineering. Reprinted with permission of John Wiley & Sons, Inc.
undesired effect on an ecosystem, but the principle is more or less implicitly behind all the ecological engineer ing methods. It is, however, possible to distinguish between ecological engineering methods that control the forcing functions and methods that change the ecosystem to be better adapted to cope with a given set of forcing functions.
Principle 2: Energy Inputs and the Capacity of Matter Storage Are Limited for Ecosystems
All the applications of ecological engineering methods must respect this principle, because the methods would not solve the environmental problems properly ifthey would rely too much on energy sources other than solar radiation or they would exceed the storage capacity of ecosystems. Pumping is of course sometimes used in constructed ecosystems for instance subsurface constructed wetlands, but the energy consumption for pumping is often modest compared with the solar energy used for photosynthesis.
The sediment of aquatic ecosystems has a limited storage capacity for nutrients, which may result in the release of nutrients from the sediment to the water if the sediment storage capacity of nutrients is exceeded. The release can, however, be reduced by use of aeration or by removal of the top 5-10 cm of the sediment (see chapters Lake Restoration, Lake Restoration Methods, and Mine Area Remediation). When the ecosystem exceeds the storage capacity for toxic substances, it is possible to remove the toxic substance by phytoremediation (see chapters Mine Area Remediation and Phytoremediation).
Principle 3: Ecosystems Are Open and Dissipative Systems
This principle implies that all ecosystems are dependent on the adjacent ecosystems. A stream that is adjacent to agricultural systems will therefore be affected by the use of fertilizers and pesticides in agriculture. It is therefore important to have buffer zones (see chapter Buffer Zones) between agriculture and natural ecosystems to reduce the effects of the man controlled agricultural ecosystems on the natural ecosystems. All uses ofconstructed ecosystems (see part Constructed Ecosystem - Imitation of Nature) are based on this principle. The idea behind agroforestry
(see chapter Agroforestry) is also rooted in this principle, because the effects from agricultural systems are reduced by mixing forests and agriculture.
The entire drainage area may contribute to deteriora tion of the water quality of a lake. A proper lake management should therefore consider the entire drai nage area in the management plan (see chapter Invasive Plants).
Principle 4: Ecosystems Have One or More Limiting Factors
This principle is rooted in Liebig's minimum law. All restoration methods (see part Restoration of Ecosystems) and all ecological management methods (see chapters Coastal Zone Management, Forest Management, Mariculture Waste Management, Stream Management, Water Cycle Management, and Watershed Management) use this principle to some extent. From the knowledge of the limiting factors, it is possible or at least easier to develop a proper strategy for the application of a restoration method or for the applica tion of ecological management in general. The principle is rooted in biochemical stoichiometry. All biological components have similar biochemical components and reactions.
Figure 1 A state variable is plotted versus a forcing function. The buffer capacity is low at point 2, but high at points 1 and 3. It is obviously beneficial in environmental management to know the relationships between important forcing functions and state variables to be able to direct the ecosystems toward high buffer capacities. Restoration methods (see part Restoration of Ecosystems) often increase the buffer capacities.
the part Restoration of Ecosystems are implicitly based on improvements of the buffer capacity.
Principle 5: Ecosystems Have Homeostatic Capability
Ecosystems are able to level out strongly variable inputs. Wetlands are for instance able to store water and thereby reduce the damage of flooding (see chapter Natural Wetlands). Buffer zones and constructed ecosystems are able to absorb high inputs of nutrients and thereby level out the nutrient concentrations in aquatic ecosystems (see chapters Buffer Zones and Natural Wetlands and part Constructed Ecosystem - Imitation of Nature). The homeostatic capability may be quantified as buffer capa city, ß, defined as the relative change in a forcing function divided by the relative change in a state variable:
where ff represents any forcing function and sv any state variable. There is a buffer capacity for each combination of forcing functions and state variables. The relationship between a forcing function and a state variable is impor tant in environmental management and particularly when ecological engineering methods are used. Figure 1 gives a possible relationship between a forcing function and a state variable. It is clear from the figure that it would be beneficial in environmental management to achieve a situation where ft is high. All the restoration methods in
Principle 6: Ecosystems Recycle the Essential Elements
Recycling implies that an element is present in ecosys tems in many different forms. For instance, nitrogen can be in the form of nitrate, ammonium, dead organic nitro gen components, and as nitrogen in living organisms. Nitrogen in the form of nitrate is very mobile, while it is less mobile in the form of ammonium that can be adsorbed by clay minerals or in the form of dead organic nitrogen that is mainly insoluble. The nitrogen in the form of living organisms is almost completely immobile. The mobility of many elements is therefore reduced when they pass ecosystems, which may explain the use of buffer zones, natural ecosystems, and constructed eco systems in ecological engineering: harmful components are retained and often in less harmful forms.
When ecological engineering methods are used, it is of course important to try to match the characteristic recy cling rates of ecosystems. The retention of nutrients is for instance limited and it is important not to overload the recycling pathways. It is, however, possible in ecological engineering to enhance recycling. A typical example is the use of biomanipulation, where the zooplankton con centration is increased, which increases the recycling rate of nutrients. All the restoration methods (see part Restoration of Ecosystems) result in more or less increased recirculation rates.
Principle 7: Ecosystems Are Pulsing Systems
The most clear ecological example is the exposure of costal marine systems to tide. It will be beneficial for instance to discharge waste water to coastal ecosystems between high and low tide, which would enhance the transportation of waste components to the open sea. All the methods presented in the part Application of Ecological Principles in Environmental Management use to some extent this principle by using the natural pulses to increase the efficiency of the method.
Principle 8: Ecosystems Are Self-Designing Systems
This principle implies that ecological engineering meth ods generally require less maintenance than for instance environmental technological methods. Therefore, it is beneficial in developing countries to apply ecological engineering methods, as they do not require sophisticated technology and regulation to achieve the required results. All ecotechnological methods are based implicitly on this principle, although the methods in the parts Use of Natural and Semi natural Ecosystems to Solve Environmental Problems and Constructed Ecosystem -Imitation of Nature use this principle directly as the use of natural and constructed ecosystems relies on the self designing ability of ecosystems, driven by solar energy.
Principle 9: Ecosystems Have Characteristic Timescale and Space Scale
A natural landscape has many small ecosystems and eco tones, as transitions between two ecosystems. It is important in ecological engineering to respect these very effective working landscape patterns. Ditches, ponds, groups of trees and bushes, and hedges are ecosys tems that can effectively - relative to their size -decompose pollutants. This principle is very important for all the methods presented in the part Application of Ecological Principles in Environmental Management.
Principle 10: Ecosystems Have Diversity
Chemical, biochemical, and biological diversity contri bute to the self designing ability of ecosystems. Higher diversity means that there are more processes and com ponents that can contribute to the development of self design. Higher diversity does not necessarily give higher buffer capacity but will inevitably give a wider spectrum of possible buffer capacities. More processes or compo nents mean that there is a higher probability that one process or component can cope with a more or less harmful forcing function. For all the methods presented in the parts Use of Natural and Semi natural Ecosystems to Solve Environmental Problems, Restoration of Ecosystems, and Constructed Ecosystem - Imitation of Nature, a high diversity may imply a higher efficiency of the methods. It is for instance considered by the use of constructed wetlands for the removal of nutrients from agriculture drainage water and by the use of phytoreme diation, where the presence of several plant species with different growth pattern, growth rate, and uptake rate of toxic components increases the overall efficiency.
Principle 11: Ecosystems Use Transition Zones (Also Called Ecotones) to Make Soft Transitions between Two Ecosystems
Nature has never a sharp transition between ecosystems, because all components and species will inevitably be exchanged between adjacent ecosystems. The transition zones will therefore have some of the characteristics of all neighboring ecosystems. The transition zones will work as buffer zones (see chapter Buffer Zones), which are able to reduce the impact between two ecosystems. The principle is used to a high extent in ecological management. Many countries have for instance legislation about the use of transition zones between arable land and urban zones on the one side and natural ecosystems for instance lakes, coastal zones, and rivers on the other side.
Principle 12: The Components of an Ecosystem Are Connected and Interrelated
The components of an ecosystem form a network that has a synergistic effect. Through the network the ecological components work together for the benefit of the ecosys tem. The higher the diversity and complexity of the network, the higher the probability of development of an effective and synergistic network. It is very important that the ecological engineering methods understand how the ecological networks work as a cooperative network and utilize the synergistic effect of the network in the application of the ecological engineering methods. It is clearly of importance for all the ecological engineering methods presented in the chapter Buffer Zones and the parts Restoration of Ecosystems, Constructed Ecosystem -Imitation of Nature, and Application of Ecological Principles in Environmental Management.
Principle 13: Ecosystems Are Not Isolated but Coupled with Other Ecosystems
The components in an ecosystem are not only connected to other components in the ecosystem but may also often be connected to components in adjacent ecosystems. It is completely in accordance with Principle 3 - Ecosystems Are Open and Dissipative Systems. The coupling to other ecosystems can be utilized beneficially by the ecological engineering methods and should under all circumstances be considered by application of all the methods in the parts Use of Natural and Semi natural Ecosystems to Solve Environmental Problems, Constructed Ecosystem - Imitation of Nature, and Application of Ecological Principles in Environmental Management. The principle implies that not only local but also regional and even global effects should be included when ecological engi neering methods are selected. The principle is of course particularly important for the chapter Landscape Planning, but it is also applicable for all the methods in the part Application of Ecological Principles in Environmental Management.
Principle 14: Ecosystems Have History, Which Is Determining the Further Development
The history of ecosystems means that an ecosystem will have a composition that reflects the history. When for instance a river has a low diversity, it may be due to a previous discharge of toxic substances. When an estuary has a high concentration of macroalgae, it may be due to a previous massive discharge of nutrients from agriculture or from waste water. The history is therefore important to consider in the application of all ecological engineering methods.
Aquatic ecosystems may show hysteretic behavior in the sense that the present structure of an ecosystem has inertia and cannot easily be changed. The hysteretic behavior is important in the use of biomanipulation as a restoration method for aquatic ecosystems (see chapter Lake Restoration Methods). Consequently, the history is particularly important for the application of this restora tion method.
Principle 15: Ecosystems and Species Are Most Vulnerable at Their Geographical Edges
This principle implies that it is important in the application of ecological engineering to consider the geo graphical spectrum of the species present in the ecosystems. The ecological engineering methods should avoid using species that are at their geographical edge. The principle should be considered by application of all the ecological engineering methods.
Principle 16: Ecosystems Are Hierarchically Organized Systems
Ecosystems are dependent on all the components, parti cularly the biological components, but they are also dependent on the landscapes, which are dependent on the regions, which again are dependent on the entire ecosphere. The ecosphere is also dependent on the regions, which are dependent on the landscapes, which again are dependent on the ecosystems that form the landscapes. It is therefore important to use holistic approaches in the application of ecological engineering methods. The ecosphere, the regions, the landscapes, and the ecosystems all work as self organizing entities and it is crucial in ecological engineering to take this into consid eration. The principle is important for all the methods presented in the part Application of Ecological Principles in Environmental Management, but it is of course of particular interest for the chapters Agroforestry, Landscape Planning, and Watershed Management, where entities consisting of several ecosystems are considered.
Principle 17: The Physical and Biological Processes Are Interactive
It is possible to change the biological processes by chan ging the physical processes and vice versa. This means that all processes influence all other processes. This prin ciple is of particular interest for all aquatic ecosystems where it is in most cases easy to change the physical processes, for instance the hydrology, and thereby obtain the desired biological effects. A characteristic example is the possibility to reduce the eutrophication of a reservoir by increasing the flow rate during spring and summer and reduce it during fall and winter. It is an example of application of the subdiscipline of ecological engineering called ecohydrology (see also chapter Ecological Engineering: Overview).
The principle is important for the chapters Coastal Zone Restoration, Estuary Restoration, Lake Restoration, Lake Restoration Methods, Riparian Zone Management and Restoration, and Stream Restoration (all about restoration of aquatic ecosystems) and for ecological management of aquatic ecosystems (see chapters Coastal Zone Management, Mariculture Waste Management, Stream Management, Water Cycle Management, and Watershed Management).
Principle 18: Ecosystems Are More Than the Sum of Their Parts and Ecosystems Have Emergent Properties
This principle is consistent with a holistic view of eco systems and also with Principle 16. The principle expresses and explains that it is necessary in the application of ecological engineering as a tool for devel opment of a better environmental strategy to consider both physical and biological processes, to take into account the entire interactive network of all ecological components, to consider the adjacent ecosystems and the entire landscape, and so on. The principle may be considered as a summary of several previous principles. It underlines that ecosystems are working as systems not as loosely connected components. It also explains the emergent properties.
Principle 19: Ecosystems Have Their (Enormous) Information Stored in the Structures
The structures include organisms and the physical structures of the landscape. It is important in ecological engineering to maintain the high level of information that is embodied in the genes of the organisms and in the structure of the networks. The information deter mines self organization, buffer capacity, homeostatic capability, diversity, (synergistic) networks, and recy cling capability. The success of application of an ecological engineering method is of course dependent on the maintenance of all these characteristics of eco systems and it is therefore crucial to protect and maintain the high level of information that is stored in ecosystems.
The design principles in the chapter Design Principles are also rooted in the 19 principles. The Overarching Principles are the thermodynamic principles and the energy flow principles, which are in accordance with Principles 2-4. Recycling and self organization men tioned as important design features are Principles 5, 6, and 8. Furthermore, it is mentioned that the forcing functions and the history - Principles 1 and 14 - must be considered for the design in ecological engineering. The design principles (see chapter Design Principles) that are applied in ecological engineering are therefore com pletely consistent with the 19 principles.
The parts Use of Natural and Semi natural Ecosystems to Solve Environmental Problems, Restoration of Ecosystems, Constructed Ecosystem - Imitation of Nature, and Application of Ecological Principles in Environmental Management present 33 different ecolo gical engineering methods.
The part Use of Natural and Semi natural Ecosystems to Solve Environmental Problems contains the first type of ecological engineering according to the classification in the chapter Ecological Engineering: Overview. Natural ecosystems are utilized to solve pollution problems, fre quently a non point pollution problem. These methods are based on the characteristic ecological properties of ecosystems, such as ecosystems recycle important ele ments, are self organizing, are organized hierarchically, have complex synergistic network with indirect effects, and have history. These methods are therefore indeed based on the 19 principles listed above.
The part Restoration of Ecosystems covers restoration methods, that is, methods that - based upon a profound knowledge of the properties of ecosystems -support and assist ecosystems to cope with a number of environmental problems. It is obvious from this explanation that the meth ods are based on the ecological principles of ecosystems.
The part Constructed Ecosystem - Imitation of Nature encompasses the third type of ecological engi neering according to the classification in the chapter Ecological Engineering: Overview - constructed ecosys tems. Here, the idea is that the valuable properties of ecosystems that are able to provide solutions to environ mental problems could be imitated. We can learn from ecosystems how to solve environmental problems or, expressed differently, we can learn from nature how to develop and apply tools in the ecological engineering tool box. The tool box could also be called soft technology - a technology that in many cases has less side effects, is more cost moderate, and more easy to operate and maintain than environmental technology. It does not mean that ecological engineering can replace environmental tech nology. In some cases, it can offer a better solution, but a proper and complete environmental management will in most cases require all four tool boxes.
The chapters Mass Cultivation of Freshwater Microalgae, Mass Production of Marine Macroalgae, and Multitrophic Integration for Sustainable Marine Aquaculture encompass different forms of what we could call aquafarming: cultivation of algae and marine aquaculture. These three chapters are included in the part Constructed Ecosystem - Imitation of Nature and are considered ecological engineering, because ecological principles are used and nature is imitated. Organic farm ing is also covered in the part Constructed Ecosystem -Imitation of Nature (see chapter Organic Farming). Organic farming is agriculture that has learnt from nature how to recycle the essential elements and avoid the use of toxic substance. These four chapters could have also been included in the part Application of Ecological Principles in Environmental Management, because they can also be considered a more ecologically sound planning of aqua culture, aqua farming, and farming. The four chapters are, however, included in the part Constructed Ecosystem -Imitation of Nature, because they are built very much on what we can learn from natural ecosystems and how we can utilize ecological principles in production systems that are controlled by man. The question in the four chapters is, How can we achieve a high production and at the same time avoid environmental problems that characterize agricultural and aquacultural production?
The last part, Application of Ecological Principles in Environmental Management, presents the ecological engi neering methods that are based on a good ecological and in most cases sustainable environmental planning. The 19 principles are of course of particular significance.
Table 1 Relationships between the ecological engineering methods and the 19 ecological principles
Buffer zones Natural wetlands Coastal zone restoration Estuary restoration Lake restoration Lake restoration methods Mine area remediation Riparian zone restoration
Stream restoration Biological control
Biological control and biopesticides
Constructed wetlands, subsurface flow
Constructed wetlands, surface flow
Sustainable marine aquaculture
Organic farming Phytoremediation Sludge technology Tillage
Coastal zone management Erosion control Forest management Invasive plants Invasive species Landscape planning Waste management Stream management Water cycle management Watershed management
Buffer Zones Natural Wetlands Coastal Zone Restoration Estuary Restoration Lake Restoration Lake Restoration Methods Mine Area Remediation Riparian Zone Management and
Restoration Stream Restoration Classical and Augmentative Biological Control
Conservation Biological Control and
Biopesticides in Agricultural Constructed Wetlands, Subsurface Flow Constructed Wetlands, Surface Flow Estuarine Ecohydrology Impoundments
Mass Cultivation of Freshwater Microalgae Mass Production of Marine Macroalgae Multitrophic Integration for Sustainable
Marine Aquaculture Organic Farming Phytoremediation Sewage Sludge Technologies Soil Movement by Tillage and Other
Agricultural Activities Agroforestry
Forest Management Invasive Plants Invasive Species Landscape Planning Mariculture Waste Management Stream Management Water Cycle Management Watershed Management
1, 3, 8, 11, S, 1S, (2), (12), (18), (19) 1, 8, S, 1S, (2), (12) 1?, 4, S, e, 1S, (2), (11), (12) 1?, 4, S, e, 1S, (2), (11), (12) 1?, 4, S, e, 1S, (2), (11), (12) e, 14, 1?, 4, S, 1S, (2), (11), (12) 4, S, e, 1S, (2), (11), (12) 1?, 4, S, e, 1S, (2), (11), (12)
1?, 4, S, e, 1S, (2), (11), (12) 1, 3, a, S, 1S, (2), (12)
S, e, 1S, (2), (11), (12) S, e, 1S, (2), (11), (12) S, e, 1S, (2), (11), (12) S, e, 1S, (2), (11), (12) S, e, 1S, (2), (11), (12) S, e, 1S, (2), (11), (12) S, e, 1S, (2), (11), (12)
S, e, 1S, (2), (11), (12) S, e, 1S, (2), (11), (12) S, e, 1S, (2), (11), (12) S, e, 1S, (2), (11), (12)
(1), (2), (T), (12) 1e, (1), (2), (Z), (12) (2), (Z), (12) (1), (2), (Z), (12) , (2), (Z), (12) , (2), (Z), (12) (1), (2), (Z), (12) (1), (2), (Z), (12) , (1), (2), (Z), (12) (1), (2), (Z), (12) (1), (2), (Z), (12)
In the previous section, the 19 basic ecological prin ciples have been listed and it has been shown how the principles are able to explain the basic ecological ideas behind the ecological engineering methods and their implementation to solve environmental problems. In this section, Table 1 gives an overview of all the 33 methods and the principles that are able to explain the application of the methods. The principles are classified into three categories in the table. The most important principles that are central for a profound understanding of the ecological methods and their function and man agement are indicated with bold numbers. The principles that are required for a more comprehensive explanation of the methods and their use in environ mental management are indicated with italic numbers. The principles that are of less importance, but still are needed for a complete understanding of the function, application, and the management of the methods are indicated in parentheses.
How to Select and Apply Ecological Engineering Methods in Practice?
The practical use of the tool box with the label 'Ecological
Engineering' follows eight steps:
1. The first step in all environmental management is to define the problem and the (eco )system that is threatened.
2. A quantification of the problem is in most cases needed to be able to develop a proper environmental manage ment strategy. Quantification implies that it is necessary to develop an ecological model that is able to give a clear relationship between various sources of the problem and the corresponding impact on the ecosystem. In other words, the model is able to inform the environmental manager as to what extent the over all problem can be reduced if one or more sources of the problem are reduced or eliminated.
3. The result of the model will in most cases be a plan about the extent to which the various sources of the problem should be reduced to obtain a desired envir onmental improvement. It is very important in this phase to use a holistic view. The result should be an integrated plan, where the interactions among various sources are considered and the ecosystem is perceived as an indivisible system with many different compo nents linked in a synergistic network.
4. For each of the sources, it should now be possible to select a tool or maybe a combination of tools from different tool boxes. It is still important in this phase to consider ecosystems as indivisible.
5. If'Ecological Engineering Tools' is one of the needed tool boxes, it is natural to ask the question in which of the four tool classes, natural ecosystems, restoration of ecosystems, constructed ecosystems, and ecological management, should one search for the right tool?
6. The question is in most cases easy to answer, while it is usually more difficult to choose the final ecological engi neering methods. It is probably not too difficult to eliminate the methods that are too expensive or cannot be applied due to practical obstacles. Still there are in most cases a few or more methods that could be applied. It is necessary to compare the economy and the results of the various methods to be able to make the final choice. The advantages and disadvantages of the 33 methods in this evaluation phase can be found in the parts Use of Natural and Semi natural Ecosystems to Solve Environmental Problems, Restoration of Ecosystems, Constructed Ecosystem - Imitation of Nature, and Application of Ecological Principles in Environmental Management.
7. When the method finally has been selected, it is necessary to make a design for the practical use of the method. Here it is recommended to apply the principles presented in the chapter Design Principles.
8. After the design, it is recommended to use the 19 principles presented above as a checklist to ensure that the method is designed and applied in accordance with sound ecological principles. Now, if the method can be accepted as ecologically applicable and sound, it is ready for implementation.
See also: Agroforestry; Buffer Zones; Classical and Augmentative Biological Control; Coastal Zone Management; Coastal Zone Restoration; Conservation Biological Control and Biopesticides in Agricultural; Constructed Wetlands, Subsurface Flow; Constructed Wetlands, Surface Flow; Design Principles; Ecological Engineering: Overview; Environmental Impact Assessment and Application - Part 1; Environmental Impact Assessment and Application - Part 2; Erosion; Estuarine Ecohydrology; Estuary Restoration; Forest Management; Impoundments; Invasive Plants; Invasive Species; Lake Restoration; Lake Restoration Methods; Landscape Planning; Mariculture Waste Management; Mass Cultivation of Freshwater Microalgae; Mass Production of Marine Macroalgae; Mine Area Remediation; Multitrophic Integration for Sustainable Marine Aquaculture; Natural Wetlands; Organic Farming; Phytoremediation; Riparian Zone Management and Restoration; Sewage Sludge Technologies; Soil Movement by Tillage and Other Agricultural Activities; Stream Management; Stream Restoration; Water Cycle Management; Watershed Management.
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USE OF NATURAL AND SEMI-NATURAL ECOSYSTEMS TO SOLVE ENVIRONMENTAL
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