globals [ Global_Temperature ; mean world temperature Temparature_Change ; rate of change in temperature applied to each patch mean_Resilience ; average tollerable temperature range mean_Influence ; average influence on patch temperature for species year ; arbitary unit time ] patches-own [ temperature ; local temperature at this location ] turtles-own [ optimum_temperature ; ideal temperature for species direction ; whether agent warms or cools patch influence ; amount by which agent warms or cools patch resilience ; difference between ideal and current temperature that species can survive ] to setup clear-all set temperature_change 0 set year 0 ask patches [ set pcolor black set temperature random-normal 0 30 ] new_species ; put some agents on empty patches reset-ticks end to go tick if count turtles = 0 [stop] set year year + 1 ask patches [set temperature temperature + Temperature_Change] ; external environmental change change_environment ; environmental change caused by life survive ; remove species that cannot survive new temperature diffuse temperature diffusion_rate new_species set Global_Temperature mean [temperature] of patches set mean_Resilience mean [Resilience] of turtles set mean_Influence mean [Influence] of turtles update_plots ask patches [if temperature > 10 [set pcolor orange]] ask patches [if temperature > 20 [set pcolor red]] ask patches [if temperature < -10 [set pcolor turquoise]] ask patches [if temperature < -20 [set pcolor cyan]] end to new_species let r 0 ask patches with [not any? turtles-here] [ set r random-float 1 if r < 0.1 [ sprout 1 [ set optimum_temperature temperature set color white let d random-float 1 if d <= 0.5 [set direction "warm" set heading 0] if d > 0.5 [set direction "cool" set heading 180] set influence random-exponential Initial_Influence set resilience random-exponential Initial_Resilience ] ] ] end to change_environment ; species changes the temperature of the patch it is on by Influence ask turtles [ if direction = "warm" [set temperature temperature + influence] if direction = "cool" [set temperature temperature - influence] ] end to survive ask turtles [ if temperature < optimum_temperature + 5 and temperature > optimum_temperature - 5 [set color green] if temperature > optimum_temperature + 5 [set color magenta] if temperature < optimum_temperature - 5 [set color blue] if temperature > optimum_temperature + resilience [die] if temperature < optimum_temperature - resilience [die] ] end ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; Plotting Procedures ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; to update_plots set-current-plot "Global_Temperature" plot Global_Temperature set-current-plot "Temperature of Patches" histogram [temperature] of patches end @#$#@#$#@ GRAPHICS-WINDOW 402 10 727 356 10 10 15.0 1 10 1 1 1 0 1 1 1 -10 10 -10 10 1 1 1 ticks 30.0 BUTTON 6 45 71 78 NIL go T 1 T OBSERVER NIL NIL NIL NIL 1 BUTTON 6 8 71 41 NIL setup NIL 1 T OBSERVER NIL NIL NIL NIL 1 SLIDER 102 10 135 160 Temperature_Change Temperature_Change -1 1 0 0.1 1 NIL VERTICAL PLOT 5 164 376 343 Global_Temperature Time Temperature 0.0 10.0 0.0 10.0 true false "" "" PENS "Global_Temperature" 1.0 0 -16777216 true "" "" MONITOR 11 98 68 143 NIL year 0 1 11 SLIDER 147 10 180 160 Initial_Resilience Initial_Resilience 0 20 6 1 1 NIL VERTICAL SLIDER 196 10 229 160 Initial_Influence Initial_Influence 0 20 3 1 1 NIL VERTICAL MONITOR 239 19 328 64 mean_Resilience mean_Resilience 2 1 11 MONITOR 238 76 327 121 mean_Influence mean_influence 2 1 11 SLIDER 341 10 374 160 diffusion_rate diffusion_rate 0 1 0.7 0.1 1 NIL VERTICAL PLOT 5 345 375 523 Temperature of Patches Temperature Number of Patches -100.0 100.0 0.0 10.0 true false "" "" PENS "default" 1.0 1 -13345367 true "" "" @#$#@#$#@ ## WHAT IS IT? A representation of an environment that can evolve feedback loops to maintain conditions to be suitable for life. SpeciesWorld is a development from the Daisyworld idea of Watson and Lovelock (1983). In Daisyworld, the white daisies thrive in warm conditions. They reflect heat which has the effect of cooling the environment. In cold conditions, there are more of the black daisies which absorb heat and warm the environment. The result is a robust feedback mechanism which, within limits, keeps global temperature within a range that is conducive for life. The question is: how did this come about. If the black daisies did better in warm conditions and the white ones preferred the cold, there would be feedback that would result in either runaway warming or coolong. SpeciesWorld depicts a situation where speicies that alter their environment in a way that promotes life have a higher chance of survival. Those that worsen their environment die out more quickly. In this way, the ecosystem evolves species which work together to counteract external environmental change. ## HOW IT WORKS The model is based on three axioms. 1 When a species first appears, it is well adapted to its environment and can only survive or adapt to an environment within a finite range of its initial state. 2 The environment changes over time. 3 Each species has an effect on the environment which may be in the same direction as the prevailing change or may be opposite to it. A simulation begins with an initial population of species represented by turtles. Each new species has an optimum_temperature which is the temperature of the patch it originates on. Species have a parameter called 'Resilience' which is the difference in temperature, above or below its optimum, that the species can tolerate before it dies. There is also an 'Influence' parameter which indicates how much warming or coolong effect the species has on its patch during each time step. Influence is also diffused around the adjacent patches. Patches have an initial temperature which is drawn from a normal distribution. At each time step, the temperature of every patch is changed by the amount shown on the Temperature_Change slider. Also at each time step, each species alters the temperature of its patch by the amount of its Influence parameter. After these two temperature changes, there is a test to determine whether the temperature of the patch is still within the species survivable temperature. Those that survive continue into the next cycle. If the temperature of the patch is too hot or too cold for the species to survive, it is removed from the simulation. Next, the current temperature of each patch is diffused into adjoining patches. Then, by a fixed probability which can be set in the program code, a new species is created in some of the empty patches. Its optimum_temperature is set to the current temperature of its patch. The model is abstract in that it is not based on any physical laws. The temperature parameter can be thought of conventionally as heat stress but is also meant to represent any environmental stress. The units of temperature are not related to any real temperature scale. The world grid can be thought of as representing physical space but also represents species space where the x y coordinates of the grid represent any number of dimensions that describe the properties of a species. ## HOW TO USE IT Press 'setup' to create the initial population. Set the 'Initial_Resilience', 'Initial_Influence' and 'diffusion_rate' parameters as required. Press 'go' to start a simulation. While the simulation is running, vary the 'Temperature_Change' parameter to see what effect it has on the population and global temperature. ## THINGS TO NOTICE See if the world grid settles down into a pattern. ## THINGS TO TRY Vary the parameters to find out the conditions needed for a stable world to evolve. What levels of resilience, influence and diffusion are needed for stability? How high a rate of temperature change can the system tolerate? Does this vary with the other parameters. ## EXTENDING THE MODEL Try different sized worlds. What happens if different parts of the world change temperature in different ways? ## CREDITS AND REFERENCES Model developed by Tony Lawson tony_lawson@btopenworld.com The Daisyworld model was first proposed and implemented by Lovelock and Andrew Watson. The original Gaia hypothesis is due to Lovelock. Watson, A.J., and J.E. Lovelock, 1983, "Biological homeostasis of the global environment: the parable of Daisyworld", Tellus 35B, 286-289. (The original paper by Watson and Lovelock introducing the Daisyworld model.) @#$#@#$#@ default true 0 Polygon -7500403 true true 150 5 40 250 150 205 260 250 airplane true 0 Polygon -7500403 true true 150 0 135 15 120 60 120 105 15 165 15 195 120 180 135 240 105 270 120 285 150 270 180 285 210 270 165 240 180 180 285 195 285 165 180 105 180 60 165 15 arrow true 0 Polygon -7500403 true true 150 0 0 150 105 150 105 293 195 293 195 150 300 150 box false 0 Polygon -7500403 true true 150 285 285 225 285 75 150 135 Polygon -7500403 true true 150 135 15 75 150 15 285 75 Polygon -7500403 true true 15 75 15 225 150 285 150 135 Line -16777216 false 150 285 150 135 Line -16777216 false 150 135 15 75 Line -16777216 false 150 135 285 75 bug true 0 Circle -7500403 true true 96 182 108 Circle -7500403 true true 110 127 80 Circle -7500403 true true 110 75 80 Line -7500403 true 150 100 80 30 Line -7500403 true 150 100 220 30 butterfly true 0 Polygon -7500403 true true 150 165 209 199 225 225 225 255 195 270 165 255 150 240 Polygon -7500403 true true 150 165 89 198 75 225 75 255 105 270 135 255 150 240 Polygon -7500403 true true 139 148 100 105 55 90 25 90 10 105 10 135 25 180 40 195 85 194 139 163 Polygon -7500403 true true 162 150 200 105 245 90 275 90 290 105 290 135 275 180 260 195 215 195 162 165 Polygon -16777216 true false 150 255 135 225 120 150 135 120 150 105 165 120 180 150 165 225 Circle -16777216 true false 135 90 30 Line -16777216 false 150 105 195 60 Line -16777216 false 150 105 105 60 car false 0 Polygon -7500403 true true 300 180 279 164 261 144 240 135 226 132 213 106 203 84 185 63 159 50 135 50 75 60 0 150 0 165 0 225 300 225 300 180 Circle -16777216 true false 180 180 90 Circle -16777216 true false 30 180 90 Polygon -16777216 true false 162 80 132 78 134 135 209 135 194 105 189 96 180 89 Circle -7500403 true true 47 195 58 Circle -7500403 true true 195 195 58 circle false 0 Circle -7500403 true true 0 0 300 circle 2 false 0 Circle -7500403 true true 0 0 300 Circle -16777216 true false 30 30 240 cow false 0 Polygon -7500403 true true 200 193 197 249 179 249 177 196 166 187 140 189 93 191 78 179 72 211 49 209 48 181 37 149 25 120 25 89 45 72 103 84 179 75 198 76 252 64 272 81 293 103 285 121 255 121 242 118 224 167 Polygon -7500403 true true 73 210 86 251 62 249 48 208 Polygon -7500403 true true 25 114 16 195 9 204 23 213 25 200 39 123 cylinder false 0 Circle -7500403 true true 0 0 300 dot false 0 Circle -7500403 true true 90 90 120 face happy false 0 Circle -7500403 true true 8 8 285 Circle -16777216 true false 60 75 60 Circle -16777216 true false 180 75 60 Polygon -16777216 true false 150 255 90 239 62 213 47 191 67 179 90 203 109 218 150 225 192 218 210 203 227 181 251 194 236 217 212 240 face neutral false 0 Circle -7500403 true true 8 7 285 Circle -16777216 true false 60 75 60 Circle -16777216 true false 180 75 60 Rectangle -16777216 true false 60 195 240 225 face sad false 0 Circle -7500403 true true 8 8 285 Circle -16777216 true false 60 75 60 Circle -16777216 true false 180 75 60 Polygon -16777216 true false 150 168 90 184 62 210 47 232 67 244 90 220 109 205 150 198 192 205 210 220 227 242 251 229 236 206 212 183 fish false 0 Polygon -1 true false 44 131 21 87 15 86 0 120 15 150 0 180 13 214 20 212 45 166 Polygon -1 true false 135 195 119 235 95 218 76 210 46 204 60 165 Polygon -1 true false 75 45 83 77 71 103 86 114 166 78 135 60 Polygon -7500403 true true 30 136 151 77 226 81 280 119 292 146 292 160 287 170 270 195 195 210 151 212 30 166 Circle -16777216 true false 215 106 30 flag false 0 Rectangle -7500403 true true 60 15 75 300 Polygon -7500403 true true 90 150 270 90 90 30 Line -7500403 true 75 135 90 135 Line -7500403 true 75 45 90 45 flower true 0 Circle -7500403 true true 30 30 240 Circle -7500403 true true 0 120 60 Circle -7500403 true true 240 120 60 Circle -7500403 true true 120 0 60 Circle -7500403 true true 120 240 60 Circle -7500403 true true 60 225 60 Circle -7500403 true true 180 225 60 Circle -7500403 true true 225 180 60 Circle -7500403 true true 15 180 60 Circle -7500403 true true 15 60 60 Circle -7500403 true true 225 60 60 Circle -7500403 true true 180 15 60 Circle -7500403 true true 60 15 60 house false 0 Rectangle -7500403 true true 45 120 255 285 Rectangle -16777216 true false 120 210 180 285 Polygon -7500403 true true 15 120 150 15 285 120 Line -16777216 false 30 120 270 120 leaf false 0 Polygon -7500403 true true 150 210 135 195 120 210 60 210 30 195 60 180 60 165 15 135 30 120 15 105 40 104 45 90 60 90 90 105 105 120 120 120 105 60 120 60 135 30 150 15 165 30 180 60 195 60 180 120 195 120 210 105 240 90 255 90 263 104 285 105 270 120 285 135 240 165 240 180 270 195 240 210 180 210 165 195 Polygon -7500403 true true 135 195 135 240 120 255 105 255 105 285 135 285 165 240 165 195 line true 0 Line -7500403 true 150 0 150 300 line half true 0 Line -7500403 true 150 0 150 150 pentagon false 0 Polygon -7500403 true true 150 15 15 120 60 285 240 285 285 120 person false 0 Circle -7500403 true true 110 5 80 Polygon -7500403 true true 105 90 120 195 90 285 105 300 135 300 150 225 165 300 195 300 210 285 180 195 195 90 Rectangle -7500403 true true 127 79 172 94 Polygon -7500403 true true 195 90 240 150 225 180 165 105 Polygon -7500403 true true 105 90 60 150 75 180 135 105 plant false 0 Rectangle -7500403 true true 135 90 165 300 Polygon -7500403 true true 135 255 90 210 45 195 75 255 135 285 Polygon -7500403 true true 165 255 210 210 255 195 225 255 165 285 Polygon -7500403 true true 135 180 90 135 45 120 75 180 135 210 Polygon -7500403 true true 165 180 165 210 225 180 255 120 210 135 Polygon -7500403 true true 135 105 90 60 45 45 75 105 135 135 Polygon -7500403 true true 165 105 165 135 225 105 255 45 210 60 Polygon -7500403 true true 135 90 120 45 150 15 180 45 165 90 square false 0 Rectangle -7500403 true true 30 30 270 270 square 2 false 0 Rectangle -7500403 true true 30 30 270 270 Rectangle -16777216 true false 60 60 240 240 star false 0 Polygon -7500403 true true 151 1 185 108 298 108 207 175 242 282 151 216 59 282 94 175 3 108 116 108 target false 0 Circle -7500403 true true 0 0 300 Circle -16777216 true false 30 30 240 Circle -7500403 true true 60 60 180 Circle -16777216 true false 90 90 120 Circle -7500403 true true 120 120 60 tree false 0 Circle -7500403 true true 118 3 94 Rectangle -6459832 true false 120 195 180 300 Circle -7500403 true true 65 21 108 Circle -7500403 true true 116 41 127 Circle -7500403 true true 45 90 120 Circle -7500403 true true 104 74 152 triangle false 0 Polygon -7500403 true true 150 30 15 255 285 255 triangle 2 false 0 Polygon -7500403 true true 150 30 15 255 285 255 Polygon -16777216 true false 151 99 225 223 75 224 truck false 0 Rectangle -7500403 true true 4 45 195 187 Polygon -7500403 true true 296 193 296 150 259 134 244 104 208 104 207 194 Rectangle -1 true false 195 60 195 105 Polygon -16777216 true false 238 112 252 141 219 141 218 112 Circle -16777216 true false 234 174 42 Rectangle -7500403 true true 181 185 214 194 Circle -16777216 true false 144 174 42 Circle -16777216 true false 24 174 42 Circle -7500403 false true 24 174 42 Circle -7500403 false true 144 174 42 Circle -7500403 false true 234 174 42 turtle true 0 Polygon -10899396 true false 215 204 240 233 246 254 228 266 215 252 193 210 Polygon -10899396 true false 195 90 225 75 245 75 260 89 269 108 261 124 240 105 225 105 210 105 Polygon -10899396 true false 105 90 75 75 55 75 40 89 31 108 39 124 60 105 75 105 90 105 Polygon -10899396 true false 132 85 134 64 107 51 108 17 150 2 192 18 192 52 169 65 172 87 Polygon -10899396 true false 85 204 60 233 54 254 72 266 85 252 107 210 Polygon -7500403 true true 119 75 179 75 209 101 224 135 220 225 175 261 128 261 81 224 74 135 88 99 wheel false 0 Circle -7500403 true true 3 3 294 Circle -16777216 true false 30 30 240 Line -7500403 true 150 285 150 15 Line -7500403 true 15 150 285 150 Circle -7500403 true true 120 120 60 Line -7500403 true 216 40 79 269 Line -7500403 true 40 84 269 221 Line -7500403 true 40 216 269 79 Line -7500403 true 84 40 221 269 x false 0 Polygon -7500403 true true 270 75 225 30 30 225 75 270 Polygon -7500403 true true 30 75 75 30 270 225 225 270 @#$#@#$#@ NetLogo 5.0 @#$#@#$#@ @#$#@#$#@ @#$#@#$#@ @#$#@#$#@ @#$#@#$#@ default 0.0 -0.2 0 0.0 1.0 0.0 1 1.0 0.0 0.2 0 0.0 1.0 link direction true 0 Line -7500403 true 150 150 90 180 Line -7500403 true 150 150 210 180 @#$#@#$#@ 0 @#$#@#$#@