Ampai Soros
Geography 491: Lab # 5
Plant Invasion and Land Use in the Galapagos Islands
For the agricultural zone:
1. What relationships exist between farm characteristics (in the attribute table) and the percent guava by farm?
The relationship between farms characteristics and percent guava in the area is that the greater the percent of guava in the farms is, the lesser the farm area is used for agriculture purpose. Although not all farms particularly the number of cattle and percent of pasture do not truly follow this relationship because there are some farm (e.g. Farm ID#2 or #1) that still have high percentages of pasture even though the guava area increases. It is possible that farmer do not need to clear the guava area for cattle since they can consume guava as an alternative food so that guava area provides some benefit for farmer and cattle, not only nuisance. However, when we take the crop area into account we can clearly see the trend of decreasing crop area with the increasing of guava area. So taking all farm characters (cattle, crop and pasture) together, it can conclude that in general the agricultural area/activities decreases when the guava percentages increase.
2. What, if any, proximity relationships exist between percent guava by field and (a) roads and (b) buildings?
That it is likely to have fewer guavas in the field containing buildings, see map:2_guava_buildings. There are 12 fields contain buildings which some fields have more than one building, percent guava in these fields range from 8 – 88% of their area. However, most of these fields have guava less than approximately 60% of their area with the exception of fields ID#18, 37, and 49 which have guava more than 80% of the area. So it can assume that the fields containing buildings are more likely to control the invasion of guava to preserve the area for agriculture, either crop or pasture. The fields with buildings which have >80% of guava indicate the abandonment of agricultural activities to other professions. Foe example, field #18 goes for tourism and fields #37 and 49 go for fishing.
About connection to the roads, there are 19 fields located near or along the roads, the percent of guava in these fields range from 12 – 86% of their area. Many fields near the roads do not have much of guava invasion, see map: 1_guava_fields. However, there are 4 fields along the roads that have guava more than 80% of the area, and their main activities are in fishing (count as tourism). From the map, it can not be definitely judged that access to the roads help decreasing or increasing the guava area because there are some fields along the roads have few percent guava while there are some fields have high percent guava. However, the most high guava area exists in the fields with the active fishing-tourism than the active agriculture. So it can conclude that tourists may contribute to the spread of guava in the area, and the percent of guava do not depend only on the access to the roads but also to the status of agriculture in those fields.
3. Are fields or farms next to abandoned fields/farms more likely to contain a higher percentage of guava? Assign each farm a category of “abandoned”, “partially abandoned”, or “active” based on percent guava present and the farm characteristics in the attribute table.
The farms next to abandoned farms are more likely to have a higher percentage of guava, see map:3_abandoned farms. The farms are assigned to three categories as show in the table below by using the percent of agricultural area as the main criteria which “active > or = 51%, partially abandoned = 26-50%, and abandoned = 0-25%. For a farm #1 which is assigned “active” although they have high percentage of guava (64.81%) because the main activities of this farm is still agriculture using 90% of the farm’s area.
Farm ID / Farm status / % agricultural area (crop + pasture) / % guava / others1 / active / 90 / 64.81
2 / active / 100 / 35.67 / Tourism
3 / active / 90 / 19.60
4 / active / 90 / 26.58
5 / partially abandoned / 40 / 70.34 / Fishing
6 / abandoned / 10 / 53.53 / Tourism
7 / active / 70 / 38.86
8 / abandoned / 20 / 74.41 / Fishing
9 / active / 80 / 29.79
10 / partially abandoned / 30 / 49.24 / Tourism
11 / active / 60 / 34.19 / Fishing
12 / active / 80 / 22.94
13 / active / 100 / 12.52
14 / abandoned / 0 / 81.15 / Fishing
15 / active / 80 / 26.28
16 / abandoned / 10 / 61.59 / Tourism
There are some farms that assigned “abandoned” though they contained about 50-60% of guava in the farms because they utilized only 10% of the area doing agriculture so I considered that they do agriculture for household consumption. Moreover these abandoned farms also have others economic opportunities in tourism and fishing so it supported the abandonment of the farms.
4. Is there spatial clustering of guava in the agricultural zone or in individual fields, and does this spatial clustering provide clues to land use practices that could affect guava distribution?
There is clustering of guava in the agricultural zone. I did a zonal analysis by majority of the area, see map: 4_clustering guava. Guava spreads diagonally from southeast to northwest direction or the other ways rounds. It is also possible that guava will invade into the eastern area of this agricultural zone, and it is shown this trend in the map. Some active farms are included in the clustering of guava so it indicates a tendency of farms abandonment in the future if those farms become less active. On the other hand this spatial clustering in the active farms also infer the association of farm animals in the guava invasion because animals consume guava and defecate throughout the farms.
For the park zone:
1. Is there a relationship between guava in the Park and distance to the agricultural zone?
The park area which is closer to the agricultural zone has more percent of guava than the further area. When the distance increases, the guava area decreases. Comparing the distance of park to the agricultural zone by classes and guava (use count field) is shown by graph below. Distances of classes in the graph indicate from closest to furthest, for example: class 1 = closest to agricultural zone; and class 10 = the furthest park area to the agricultural zone.
2. Is there a relationship between guava distribution in the park and percent guava in the fields bordering the park?
There is a trend that guava distribution in the park increases with the increasing of guava in the fields bordering the park; see graph below and map: 6_border_field_park-gauva. Although some area in the park do not follow this trend but most of them are more likely to follow this tendency.
3. How about between guava distribution in the park and characteristics of farms bordering the Park?
The guava in park area has a tendency to increase when guava in the bordering farms increases, similar to a relationship between park’s guava distribution and its bordering fields: see graph below. The most dense guava area in the park (maximum cell counts in the Count field) is the area connected to farm#6 which is abandoned farm using only 10% of the farm area for agriculture and do tourism. So we can assume that the guava invasion in the park will be more severe if the park connected to an abandoned farm.
Summary of Guava invasion in the Isabela Island:
Guava invasion in the Isabela Island is become a potential problem for both natural preserved area in the park and agricultural zone. Since guava is notorious and persists in all kind of environment then it is difficult to eradicate permanently. In the Isabela Island, the invasion of guava is leading to the abandonment of agricultural area that eventually makes the situation getting worse. Unlike the active farms, the guava in the abandoned farms can spread uncontrolled in all direction. Farm animals, cattle and pigs, also associate to the distribution of guava in farms as the information shows that farms which concentrate in cattle and pasture have higher percentage of guava (e.g. farm#1). Other factors that considered as driving forces of guava invasion are tourism and road networks in the area which contribute to the spread of guava along the roads and tourists paths.