Cameron Taylor
Lab 5
For the agricultural zone
1. What relationships exist between farm characteristics (in the attribute table) and the percent guava by farm?
In using the background information supplied at the beginning of the lab and comparing attribute tables there are several relationships that exist between farm characteristics and the percent guava by farm. To begin with I looked at when the last year that the farm was cleared to see how quickly this invasive plant grows. As shown in Figure 1 the earliest clearing was in 1985 and by the time the data was collected 80% was already reclaimed by guava. A second relationship (Figure 2) shows that if a farm has crops it has less average percent guava than farms that do have crops. Another relationship is between cattle , as mentioned in the lab background guava seeds can be spread through droppings but in looking at the relationship between average percent guava and number of cattle (Figure 3) on average the more cattle the lower percentage of guava. This could be explained by that cows are constantly grazing and could be eating the guava before it can fully grow. Finally the most important relationship is between other livelihoods practiced by farm residents and average percent guava (Figure 4). If a farmer is involved in fishing or tourism they are more likely to have a higher percentage of guava. This could be explained by they are busier with other things besides tending to their land, the land then becomes abandoned and increases the chance in guava distribution and severity of invasion.
2. What, if any, proximity relationships exist between percent guava by field and (a) roads and (b) buildings?
I “selected by location” fields that intersect with roads and buildings. Out of the selected fields that intersected with roads or buildings, mean percent of guava was 33.7% while fields that were not near buildings or roads, their mean percent guava was 37.3%. This shows that the closer a field is to either a road or a building the less likely it is going to have guava nearby. Since people are using roads and going in and out of buildings the plant has less of a chance to survive. But in areas that are not used often and hidden the invasive species thrives.
3. Assign each farm a category of “abandoned,” “partially abandoned,” or “active” based on percent guava present and the farm characteristics in the attribute table. Are fields or farms next to abandoned fields/farms more likely to contain a higher percentage of guava?
Criteria for Abandoned-
Percent Guava is greater than 50%, the sum of percentage crops+pasture is less than 40%, and farmer has another livelihood which includes tourism or fishing.
Criteria for Partially Abandoned-
Percent Guava is between 65%-30%, crops+pasture is between 50%-60%, and farmer may have another livelihood.
Criteria for Active-
Percent Guava is less than 30%, crops+pasture is 80%-100%, and farmer does not have another livelihood.
In total
Status / Count / Average cattle / Average Crops / Average Pasture / Average %GuavaAbandoned / 5 / 5 / 6 / 10 / 68%
Partially abandoned / 5 / 20 / 16 / 54 / 46%
Active / 6 / 27.5 / 23.3 / 63.3 / 23%
There is a relationship between farms next to abandoned farms being more likely to contain a higher percentage of guava. As shown in Map 1 farms with more guava are clustered near the bottom of the agricultural area which means that the fields with more guava have an influence on surrounding fields.
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 a spatial cluster of guava in the agricultural zone as compared to the rest of the park. This is caused by the lack of natural vegetation which allows for the invasive species to take over. When specifically looking at individual fields, as shown in Map 2, there is not a high spatial clustering of guava but a clustering does exist. This yields clues to land use practices that affect guava distribution. When the land is abandoned or not used for crops or cattle it becomes overrun with guava. Also fields with higher percentages of guava usually have not been clear cut since the 1990’s. Taking better care of the land by either clear cutting it or maintaining crops/cattle lessens the chance of guava spreading.
For the Park zone
5. Is there a relationship between guava in the Park and distance to the agricultural zone?
As shown in Figure 5 there is a relationship between guava in the Park and distance to agricultural zones. The further one is from the agricultural zone the fewer percentage of guava. This is because when the land is cleared for agricultural land it exposes the ground to the guava seeds. When these seeds are out in the open they are more likely to survive because there is less competition. However, when you leave the agricultural zone it transitions into more wooded and a native shrub areas, which makes it harder for guava to multiple and prosper.
6. Is there a relationship between guava distribution in the Park and percent guava in fields bordering the park?
As shown in Figure 6 there is a relationship between guava distribution in the park and percent guava in fields bordering the park. Using the allocation tool I was able to allocate guava pixels in the park to the nearest field in the agricultural zone. This then let me compare numbers of guava pixels in those fields to the number of park guava pixels allocated to the fields. This is caused by movement and expansion. As more people enter the park and use trials to visit the agricultural zone they then spread the guava to the more places in the park, particularly in bordering fields.
7. How about between guava distribution in the park and characteristics of farms bordering the Park?
There is also a relationship between guava distribution in the park and characteristics of farms bordering the park. Out of the farms whose farmer takes part in other livelihoods such as fishing or tourism, 75%are farms bordering the park. This causes there land to be inactive and have higher rates of Guava. Out of the partially active and abandoned farms 80% are on the border of the agricultural zone which further leads to the invasion of guava into the park. Also looking at Figure 7 the higher the count of guava the more pixels it has allocated meaning closer to the border. So there is a positive correlation between guava pixels in the park and total guava count at the farms.
Summary of the Guava Invasion in the Galapagos Islands
As explained in the lab background, the Galapagos Islands is renowned for its scientific importance and history but because of surrounding beauty and isolation it is being damaged by increased number of tourist and punished by bad farming practices. After answering the preliminary questions throughout the lab, guava invasion seems to be most affected by tourism and the effects that tourism has on the economy of the island. The key results from my GIS analysis that explains the spread is as follows. From the farm level many farmers are abandoning their livelihoods as farmers because of the pull factor to take part in other jobs such as tourism or fishing. This leaves the fields abandoned and increases the growth and spread of guava. This then causes the guava to spread and affect other farms that are still trying to grow crops. There is also a feedback between land use and invasion from when a farmer tends to the land by clear cutting it and growing crops it decreases the chance of guava spreading (as seen in Figures 1-4). Tourism also affects guava because they are spreading the guava further and further beyond the agricultural zone. As tourist walk on trials and sightsee in the agricultural zone they are carrying the seeds on their shoes and transporting the seeds via horse droppings. As talked about in question 6 there is a trend between the guava in bordering fields and throughout the park. Though there is more guava in the agricultural zone than the park zone you can see the spreading of the species. Since the guava will not spread as quickly in the park zone than in the agricultural zone due to thicker vegetation and species competition it is important to try and contain the guava inside the agricultural zone so that you can try to eradicate it there. By making farmers and tourist more aware that they are spreading the species by having checkpoints and boot cleaning stations they could better stop the spread. To further test my hypothesis that the main cause of guava invasion is tourism addition data that could be useful would be tourism rates and numbers. By looking at how many people are coming into the park and having better records of where they are going we could better analysis that tourism is the main culprit.
Appendix
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7